Picasso beads have a mottled coating on the surface.  It can be one color or a mixture of colors.  The coating is not synthetic but rather metal-based, and is sprayed onto the beads (and not heat-sealed).  The concept here is that the beads look painted or arty.  I used to use the term "picasso" to refer only to opaque beads with such a coating, but now I sometimes use it for translucent beads with such a coating.

"Cinder" beads have black specks or "cinders" embedded in the surface.  Beads which merely have speckles in the coating wouldn't be called cinder beads.  I carry only one style of cinder beads and one style of speckled beads.

"Givre" beads are clear or translucent beads that have a cloud of opaque color in the center or in part of the bead.  Some sellers use the term "givre" to refer to any colored bead which has the slightest bit of clear glass in it, but that isn't accurate.  From what I have read, the term was first used by Swarovski to describe such beads (although I believe the Swarovski beads came in just the color white).  The word is from the French and means "frosty".

"Porphyr" refers to beads which have two or more colors in a striped or swirled pattern.  One of the colors is usually white and is swirled together with the other color.  One supplier that I know refers to any bead that has (1) clear glass, (2) white glass and (3) colored glass as a porphyr bead.  Please note that this term is not in wide use.

These are considered porphyr beads by some people:

The term "tortoise" originally meant amber-colored beads with black stripes in them (like the beads on the left, below), but now it refers to any translucent bead with dark stripes.  The stripes in tortoise beads are often horizontal, but not always.  They should be in a somewhat parallel pattern and not be just random swirls.  The green beads on the right have poorly formed stripes, but I still refer to them as tortoise beads.

"Confetti" beads are tortoise beads with multicolored stripes, typically pink, blue and green.  Sometimes the stripes are uniform and sometimes they are poorly formed.

"Two-tone" beads are simply beads with two colors, either in the glass or in the coating.  A bead which has one color in the glass and the other color in the coating would simply be called a coated bead.  Beads which are a combination of clear glass with one color are not two-tone.  Beads which are a combination of white with another color, or black with another color, can be called "two-tone" if that is your preference.  Personally, I don't view clear, white or black as being colors.

Of the beads shown below, the first two (which have a cloud of one color inside another) could be called givre beads, although I prefer "two-tone" because the inner color is not opaque.  The fifth bead is a subtle mixture and may be hard to see:  aqua and green.

I use the term "multicolored" for beads which have three or more colors in each bead.

When beads of different colors are mixed together in the same lot, I just called them "mixed".

The term "swirl" is very generic, and I hadn't intended to define it.  But now that I am adding pictures to this article, I think I should include it.  I use the term "swirl" to refer to any bead which has loose, non-uniform stripes of color in the beads.  If the stripes are very uniform, then I simply call them "striped" (although such beads can sometimes be called "tortoise").  Please note that the purple beads below are considered "porphyr" beads by some, and might be called "tortoise" by others.

"Lined" beads have either metal (usually silver, in which case they're called "silver-lined") or color (usually paint) in the holes.  In the pictures below, the beads on the left are faceted pony beads with large holes.  The second beads are aqua with purple in the holes, and the third and fourth beads are faceted.

"Crackle" beads are beads which were dipped into water while they were still hot, causing them to crack.  I am not talking about one large crack, but many small cracks throughout the beads, giving the beads a particular appearance.  Some people just adore crackle beads, but crackle beads sometimes do break apart, so I consider them to be unreliable.

Shapes

The most common bead shape is the "round" bead.  Actually, the correct term is "spherical" but everyone just says "round".

"Faceted" beads are smooth beads (of any shape) which have had facets cut in the surface.  Facets can be cut by hand (in which case the artisan uses a box-like cutting device which cuts facets on many beads at once) or by machine.  Machine-cut beads have facets that are not as perfect, so they are then fire-polished (pulled through high heat to cause the bead surface to become molten, which makes them shiny).  All the faceted beads below are machine-cut and fire-polished.  The blue "3-cut" beads on the right are only partially faceted.

"Window" or "table-cut" or simply "cut" beads are smooth beads which have two or more facets cut into the smooth glass.  On the non-window part of the bead, there is usually some kind of coating (picasso or gold, for example) or some other effect, such as a matte finish.  If there are only two cuts which are parallel, I refer to them as "table-cut" beads.  If there are 3 or more cuts, I refer to them as "3-cut" or "4-cut" or "5-cut", etc.

A "cathedral" bead has facets around the middle of the bead.  The top and the bottom of the bead will be patterned glass, often with a gold or silver coating.  They are called "cathedral" beads because there is a gothic quality to the shape.

"Cylindrical" or "cylinder" beads are, well, cylindrical.  If the hole runs the long way, and if the beads are much longer than they are wide, they can also be called "tube" beads.  If the cylinders have 5 sides, they are called "atlas" beads (I think that atlas beads were named for Atlas-brand pencils).  If they have 4 sides, they can be called "stick" beads.  If they are stick-shaped but not too long, they can be called "rectangular" or "rectangles".  If the beads are cylindrical but have angled sides, they can be called "angular tubes".

"Cube" beads are, of course, cube-shaped.  The hole runs through the middle of one side to the middle of the opposite side.  When the hole runs from corner to corner, they can be called "diagonal cube" beads.  Many people call cube beads "square" beads (as I did when I first started my business), but for a bead to be square, it must be flat in one dimension.  If a flat square bead has the hole running from corner to corner, then it can be called a "diamond" bead.  However, diamond beads are usually longer than they are wide.  Diamonds look similar to bicone beads, but diamonds are flat and bicone beads aren't.  If a diamon bead has some additional attribute – such as curves – then you can add that to the description.

"Baroque" beads are what you might call nugget-shaped.  They are more-or-less round, but also uneven.  Of course, molded baroque beads are all the same shape, but a good baroque bead has doesn't look uniform from one to the next.

"Pinched oval" beads are oval but have a flat or angular depression on two or more sides.  They look somewhat similar to baroque beads, and I am guilty of calling them "baroque" beads because more people search for baroque beads than pinched-oval beads.

A "nugget" bead is like baroque bead except that it is shorter than it is wide.  In my opinion, the gold-colored beads below are a little too perfectly shaped (almost like rondels); the purple beads right above them are shaped more like nugget beads.

"Rondel" or "rondelle" beads are, like nugget beads, wider than they are long.  They differ from nugget beads in that they are much flatter, like a disk, and their shape is perfect and not uneven.  Please note that "rondell" and "roundel" are incorrect spellings.  The green rondels below are faceted, but they are still rondels.

"Fluted" beads (also called "melon" beads by some) have grooves in the sides.

"Oval" beads can range from rice-shaped beads to football-shaped beads to barrel-shaped beads.  Immediately above, the two beads on the right are fluted ovals.

"Flat oval" beads are simply ovals that are flattened.  In the pictures below, the first oval is the classic shape, the second oval is elongated, the third oval is squarish, the fourth oval is in the classic shape but a little more squat, and the fifth oval is wider than most, almost round.

"Bicone" beads are a little hard to explain.  Imagine a four-sided cone, and then put two of them together at the wide end, and you have a bicone.

"Sliding diamond" beads are a curious shape.  If you take two diamonds (a diamond is a square on its corner) and separate them slightly, and then fill in the space between them, that is a sliding diamond.

Other types

There are other types of beads that I could list here, but in most cases it is obvious from the name what they are.  For example, I don't think I need to post pictures of "leaf beads" (beads in the shape of a leaf).  Embossed beads would be any bead with a raised pattern on them.

What are fire-polished beads?

Round beads are cut by machine to create the facets, and then the beads are drawn through high heat to "polish" them.  The heat causes the surface of the beads to turn molten, thus making them shiny when the glass cools.  Fire-polished beads are not as fine as crystal beads that have been polished by other methods, but they are much cheaper.  Some of the facets on fire-polished beads may look uneven because the glass doesn't cool evenly, or because the molten glass "pooled" before cooling.  Also, the ends of the beads (the portion around the hole) will be round because the machines don't cut there.  The very best crystal beads will have uniform facets and will have facets everywhere, including the ends around the holes.  But in actual use, no one looks very closely at beads, so there is really no reason not to use fire-polished beads.  If, however, you are making a necklace with expensive components – real gold findings, lampwork beads, precious or semi-precious stones, etc. – you may want to use only the best crystal beads.  That generally means using Swarovski beads.  I don't carry Swarovski beads, but I may in the future.

Fire-polishing is used for other purposes than smoothing out facets.  Some beads are coated and then fire-polished to set the coating on the bead.  Sometimes this process bonds the coating to the glass so that the coating is permanent (as in vitrail and luster beads), but the coating won't get bonded to the glass if it is synthetic.

What are coated and lined beads?

Coated beads can be coated in different ways.  If the coating is fire-polished after it is applied, it will be more durable than if it is just sprayed on.

Most coatings contain metal and will bond to the glass when they are fire-polished, and those coatings should never come off.  This group includes vitrail and luster coatings.  AB coatings ("aurora borealis") are primarily silver-colored and are usually sprayed on part of each bead.  AB coatings are not heat-sealed and will come off with time.  Swarovski makes beads with AB coatings on them that wear off; and I figured that if AB coatings are good enough for Swarovski, they are good enough for me to carry.

Some coatings, such as luster coatings, may be sprayed onto the beads right after the beads have come from the presser, and while they are still hot.  Such coatings should be durable.  I have never seen Czech beads being made, and I cannot personally tell whether a coating was sprayed on while the beads were still hot, or whether the beads were fire-polished (sent through the oven) to seal the coating.

I sometimes buy beads that have a polymer-based (plastic) coating sprayed on them; such coatings may or may not be very durable (it depends on the bead).  It used to be that fire-polishing was only used to bond metal-based coatings to beads, but now it is sometimes used to set synthetic coatings as well.  The fire-polishing cures and hardens the coating, but it may still be soft around the holes and can be scraped off with a fingernail.

Please note that Czech glass pearls have polymer-based coatings that are not heat-sealed.  I don't know how durable those coatings are (although I recently handled a necklace made of Czech pearls that was more than a decade old, and it was fine).  If the pearls have sharp edges on them (such as cube-shaped beads have), then the coating may split at the edges – that is why I no longer carry cube-shaped pearls.

Lined beads have holes running through them that have been painted.  I don't know much about the types of paint used, or whether they are durable.  Many seedbeads are made with painted holes.  My experience with seedbeads indicates that the color of lined beads will eventually fade, and the paint may eventually fall out of the holes.  Gold-lined and silver-lined beads are usually lined with metallic paints and not the actual metals, although some very expensive beads may have real gold and silver in them (frankly, I'm not sure).

What is a "druk"?

A druk is a round bead (i.e., spherical).  I believe the word is Czech, but I am not sure.