First of all, the basics of CD'ing. Every diaper needs 2 parts - the absorbant part and the waterproof part. Some diapers come as one or both parts.
CD = Cloth Diaper
AIO = All In One - these are diapers that are one piece, and have the absorbant and the waterproof parts. They are shaped like and as easy to use as disposable diapers. They are the most dad and babysitter friendly! They have elastic in the legs and close with snaps or velcro.
Aplix = the generic name for velcro
Contour = This is the absorbant part of the diaper. It is shaped like a diaper but doesnt have elastic, velcro or snaps. It needs a diaper cover.
Diaper Cover = this is the waterproof part of the diaper. This can go over a fitted, prefold, flat or contour. They come in PUL, nylon or wool.
Fitted = These are the absorbant part of the diaper. They are shaped like a diaper, have elastic in the legs and close with velcro or snaps. These need a cover to be waterproof.
Flat = this is the original cloth diaper. It is a long thin piece of fabric that has to be folded in various ways to make it absorbant and fit your baby. It requires a cover.
Longies = these are wool or fleece diaper covers that also serve as pants. The absorbant material
One-Size = these diapers are meant to be used by your baby throughout his/her diapering career. They are made to be adjustable to get bigger as the baby grows.
Pockets = these diapers have a (usually) PUL outer and a material (such as fleece) inner. They have one edge open which creates a pocket to add an insert. The pocket is the waterproof part. You have to add an insert or doubler to make it absorbant. You can add more inserts the more absorbant you want the diaper to be, such as for night-time use.
Prefold = these are what you might orginially think of when you think of your grandmother's cloth diapers. They're called prefolds, because unlike Flats, they're sewn with layers to make them absorbant. Most prefolds are 4x8x4 or 4x6x4. This is the ply or layers of fabric. 4x8x4 means the outer sections have 4 layers of fabric and the middle section is 8 ply. Prefolds can be folded in various ways and put in a diaper cover.
PUL = polyurethane laminate - usually a polyester or cotton fabric laminated with polyurethane film = NOT plastic!! - This material is used to make many types of diapers waterproof. This can be used for diaper covers, AIO, and pockets.
Shorties = these are wool or fleece diaper covers that look like shorts. The natural material is absorbant and makes the diaper waterproof. An absorbant material, such as a prefold or fitted, is needed underneath.
Skirties = these are like shorties but have little skirts over the shorts
Snappi = this invention is the next best thing since sliced bread! It replaces the diaper pin so now dad has no excuse to not change a diaper! It is T-shaped and has little teeth on the edges which grab the fabric to hold it together. The teeth are sharp, so keep it away from your baby when not in use. It can be used with prefolds, flats and contours.Soakers = these are diaper covers made out of wool or fleece that resemble underwear or shorts. The natural material is absorbant and makes the diaper waterproof. An absorbant material, such as a prefold or fitted, is needed underneath the soaker.
Sposies = disposables
Let me know if I'm missing something!