PUL - is polyurethanelaminate (sp) It's a kind of breathable plastic
the m is modern
ofsm = one size fits most (sometimes companies will say OSFA A=all, but most is more accurate)

My preferences:

Flat nappies with a snug cover for newborns

For older babies/toddlers, I like me a good pocket because I'm lazy

Welcome to the world of cloth. Just take is slow, don't buy too many things all at once - it's good to try a few different types and systems to see which suits you and your baby best. Oh, and ejoy!