As far as the lingo and whats what, I thought I'd never get my head around it but it's simple.
You have fitted nappies which work like the old terry ones but they dont need folding and have velcro/applix or poppers to fasten. These need a wrap which is the equivalent of the old plastic pants only modern breathable materials.
You have AIO - All in ones - and they are basically everything above in one. They have the absorbent part in the waterproof part and you chuck the lot in the wash.
The other main ones are called pockets. They are the outer waterproof part with a pocket that you insert the absorbent 'boosters' or 'inserts' in to.
Everything else is a slight variation on the same themes.
Liners are a different thing and they are either flushable or fleece. I use fleece after finding flushables a pain. They just scrunch up in the nappy. The fleece also keeps them dry as moisture only goes one way but they arent a 'must have'.
As far as what to get I was lucky with Hebe to hit a nappy that I bought for Sid and it turned out to fit her perfectly. One size or birth to potty (BTP) are great when they are older as they are basically a large nappy that can be poppered down smaller. With Sid I started buying different ones while I was pregnant. I got a few of the different types and after a few weeks I started to get where I began to have a preference. Then I started to get more of the type I liked!
Pre owned is the way to start IMO. Buy an one of each you fancy trying and take it from there. New nappies need washing up to 8 times to get up to full absorbancy so thats done when you buy a used one!
http://www.clothnappytree.com/forum/viewforum.php?f=56&sid=9531fc270e51ec862decfc104b172a63