The world of cloth diapers can be pretty confusing, with all the acronyms used - OS, AIO, AI2 - what does it all mean? Here is a list of the most important terms you will encounter on your journey through the land of cloth.
AIO (All-in-one) - These are the most like disposables. Easy to put on, easy to take off; the absorbent part and waterproofing is sewn together. Because everything is sewn together they generally take longer to dry though and can be more difficult to get all the layers clean.
AI2 (All-in-two) - These are similar to the AIO, except that the absorbent pad in the nappy can be removed, allowing for easier washing and faster drying. Also more economical than AIOs.
Pocket nappy - The middle-ground and most popular option. Easy to put on, easy to take off, but does require some assembly when coming out of the wash as you have to stuff the pocket opening in the nappy with an absorbent pad (usually microfibre, but can also be bamboo or hemp or a mixture). They dry fast and are easy to clean.
Hybrid fitted - This falls between an AIO and a fitted. Instead of a layer of PUL there is a hidden layer of fleece which makes it semi-waterproof. They can be used without a cover during the day (unless you have a very heavy wetter) and with a cover at night. Many of the WAHMs make hybrid fitted nappies and they tend to be one of the more expensive cloth nappy options. They are show-off nappies and usually very absorbent, but can take long to dry.
Fitted nappy - Somewhere between an AIO and a prefold. These nappies do not have a waterproof outer shell so they require a cover, in all other ways they look similar to an AIO and fasten easily around baby with velcro or snaps. They are easy to use, economical and easy to wash but can take long to dry as they are normally quite thick.
Prefold - A rectangle usually made of cotton (but can include hemp too), these have to be snappi'd or pinned onto baby and require a cover. If used with certain covers (Thirsties, etc.) They can be simply trifolded (folded into thirds) and placed in the cover to put onto baby without using any pins or snappis. This is the most economical option as you don't need to buy as many covers and are the easiest to wash as well. They are quick to dry as well.
Flat - A square of single layer fabric which has to be folded and snappi'd or pinned around your baby. An example of this is the old terry squares. There are many more flat options available these days and they can be a very trim and economical option. Flats are considered to be of the more absorbent options and fairly quick drying.
Cover - Waterproof layer to stop the wetness from a prefold or fitted to get onto baby's clothes. Modern covers are usually made from PUL (poly-urethane laminate) which allows baby's skin to breathe. Covers can also be made of fleece or wool.
OS - One-size. Also called OSFA (one size fits all). This usually means that the nappy will fit from birth to potty training, though you will find that most one-size nappies won't fit properly at birth and you will either need a different nappy solution for the first month or two (disposables or newborn prefolds) or have to contend with a very bulky nappy on a newborn which will probably be prone to leaks as well, due to gaping around the legs.