OK, I'll see if I can help you...
the outer waterproof bit should be called a wrap or cover- e.g.a Totsbots wrap will be made of either fleece or PUL (polyurethane laminate) and needs a nappy inside it. If you want to, you can line the nappy with a liner- flushable liners get chucked, fleece liners can be washed and re-used. the advantage of these is that wee passes through them into the nappy, and the skin is kept dry.
So, if the description includes "PUL" it is already waterproof.
Some nappies are "all-in-one", which means that the nappy, wrap and liner are sewn together, making them very easy to use, but more expensive and less versatile. they take quite a while to dry , too.
Some nappies are "pocket nappies" or "stuffables" (although that term has been trademarked by Nature Babies). This means that the wrap and liner are stictched together, and there isa pocket to insert an absorbent nappy.
I have to say I'm a blatant Totsbots fan, but you'll get a lot of other recommendations, too. Got to go, dinner on table.
HTH