Pocket nappies consist of a waterproof outer and usually a fleece or cotton inner. There is an opening along the back of the nappy through which you can insert absorbency. You can also lay the absorbency on top. Usually the outer part is very quick drying allowing for more inserts to shells to be purchased and used while your other inserts dry. They are not a simple to use as an all in one nappy as the inserts need removing before washing and then replacing before you can use it again (not if laid on top). Lots of people love the versatility of pocket nappies and how quickly they dry.