I am taking this from The Diaper Jungle because it's such a great desciption of them. I thought they might help out any moms on here trying to understand cloth diapers.
Cloth Diaper Terminology
AIOs, pockets, fitteds, doublers, soakers...it can get a little confusing for a cloth newbie. Let us help you sort it all out. On this page we provide definitions for all the major cloth diapering products.
AIO - All-In-One - AIOs are fitted diapers that have a waterproof outer layer. This layer usually consists of fabric that has a PUL (PolyUrethane Laminate) backing, polar fleece such as Windpro, or wool. These are the closest in similarity to disposable diapers since they are a one-piece diapering system. The absorbent soaker material is often sewn into the diaper; it may also be detachable.
AI2 - All-In-Two - AI2s are very similar to AIOs with the exception that the absorbent soaker material is not attached to the diaper in any way. The soaker is usually a second, separate piece that must be used in conjunction with the diaper. The drying time for these diapers is shorter than the traditional AIO.
Contour Diapers - Contours are hourglass shaped diapers with no elastic in the legs or back. They must be held together with a SNAPPI® Diaper Fastener, pins, or a diaper cover. These diapers are not waterproof, so a cover will be needed.
Diaper Covers - Covers come in many styles and shapes, but their function is to provide a waterproof outer layer for non-waterproof diapers (all except AIOs). They are often fitted with elastic and fasten with snaps or Velcro. Some covers pull-up, like underpants. Diaper covers are usually made from polyester, Polyurethane laminates (PUL), waterproof nylon, fleece or wool.
DSQ ~ This stands for Diaper Service Quality. Diaper services use only the highest quality materials because their diapers must stand up to a lot of use and a lot of laundering. DSQ is usually used in reference to high quality pre-fold diapers.
Doublers – Doublers are pad-like absorbent soakers that can be added to a diaper to increase absorbency. They are especially useful during times when you know extra protection is needed, perhaps at night time.
Flats - These one-layer diapers, generally made out of 100% cotton gauze, are the most "old-fashioned" choice. They dry quickly and fit a large range of sizes. Folding and pinning are required.
Fitted Diapers - Fitted diapers closely resemble disposable diapers. They are contoured and fitted with elastic around the legs and back. They fasten with Velcro or snaps, and a waterproof cover must be worn over them. They are the next step up from flat pre-fold diapers and much easier to use.
Hook & Loop - These are Velcro-like closures. Since the Velcro brand is not very soft, many diaper makers use Aplix or Touchtape brand hook and loop.
Liners - Liners are thin layers of cloth or paper that are placed inside the diaper to aid in the cleaning of solid waste. In the case of paper liners, the solid waste collected on the liner can be removed from the soiled diaper and either thrown away or flushed. Cloth liners must be washed, but aid in laundering. They also help protect the actual diaper from staining.
Longies - These are also called soaker pants or sweater pants. Longies are wool soakers that have longer legs to form pants. They are great for winter time.
Pre-folds - Pre-fold diapers are rectangular shaped diapers that must be folded into the shape of a diaper. They are similar to flats, but have multiple layers with more layering in the middle. They often have 2-4 layers of absorbent material on either side and 6-8 layers in the middle. The amount of layers varies according to the size you choose, generally ranging from preemie to toddler. You may see a pre-fold described as being 4x8x4. This describes how many layers there are in the outer and inner sections: 4 layers in both outer sections and 8 layers in the inner or middle section. Pre-folds are usually the cheapest type of cloth diapers available. They must be used in conjunction with a cover.
Pocket Diapers - Pocket diapers are like AIOs orAI2s. They have an outer layer of a waterproof material and an inner layer of a stay dry material, like microfleece or suedecloth. They close with Velcro or snaps. They have a pocket opening that allows for the absorbent material to be stuffed in the pocket during use and then removed for laundering. The absorbent material for stuffing can be an insert that comes with the diaper or a pre-fold or doubler. Some moms use terry wash cloths. Pocket diapers are a popular choice among cloth diapering moms because you can customize the amount of absorbent material.
Snappi® - A plastic mechanism that fastens a cloth diapers. These are often used instead of diaper pins.
Soaker Pants - See Longies
Soakers - The term soaker can be applied two ways. It often refers to the absorbent middle part of the diaper that absorbs the moisture when a baby wets. Soakers may be sewn inside the diaper, partially sewn to form a flap, snapped in inside the diaper, or simply laid inside the diaper. The term soaker is also used in reference to wool diaper covers.
Wool In One (WIO) - This is a All-In-One (AIO) but made with wool outer fabric.
Cloth Diaper Lingo and Abbreviations
As you you enter the world of cloth diapering via online message boards and discussion groups, you might get a little lost. Cloth diapers tend to have their own lingo when discussed among friends...so we have compiled a list of popular words and abbreviations related to cloth diapering that may help you figure out what is being said! Some of these are not specific to cloth diapering but seem to come up frequently in online conversations and are rather universal in nature. Enjoy!
AIO - All in One diaper
AI2 - All in Two diaper
AP - Attachment parenting
BF - Breastfeed
BTDT - Been there done that
BTW - By the way
CD - cloth diaper
Crunchy - Natural lifestyle
CPF - Chinese prefold
DSQ - Diaper service quality
EC - Excellent condition
F&C - Free & Clear (used referring to detergents)
FLer - Front loader washing machine
FS - For sale
FSOT - For sale or trade
FYI - For your information
Hyena - A term for hard to get, popular diapers that are stalked by diaper hungry moms
IPF - Indian Prefold
IMO - In my opinion
ISO - In search of
ITA - I totally agree
KWIM - Know what I mean
LMK - Let me know
LO - Little one
LOL - Laugh out loud
NAK - Nursing at Keyboard
PUL - polyurethane laminate, a material used to make diaper covers/wraps
ROFLOL - rolling on the floor, laughing out loud
SAHM - stay-at-home mom
TLer - Top loader washing machine
WAHM - work-at-home mom
Diaper Brands Commonly Referred To With Abbreviations:
BG - bumGenius
FM - Fluffy Mail
FMBG - Full Moon Baby Gear
FB - Fuzzi Bunz
HH - Happy Heiny's
LC - Little Caboose
ME - Motherease
GAD - Green Acre Designs
SEZ - Snap E-Z