Pocket, empty nappy that you completely stuff to your requirements. Some examples... fuzzi bunz, bumgenius one size, weenotions one size, weenotions side snap etc...
All in one, are pre-stuffed so you just take it off and on like a disposable. Examples... tots bots easyfits, bumgenius organic all in one,
All in 2, are an outer shell with snap in soakers that can be changed without having change the outer shell unless its dirty. So you take the soaker out and put a clean one in the same outer shell.
Some examples... weenotions AI2, weehuggers etc
Hope that helps!