Pocket nappies were our nappy of choice when our daughter was in nappies. They are easy to use and really easy to boost, which makes them a very popular starter nappy.
They consist of a waterproof outer shell which usually has a stay dry lining as an inner and an opening (the pocket) where the two meet at the back. The lining is not absorbent, it is usually fleece which helps keep baby dry, and you use the pocket to add the absorbency to the nappy with inserts.
These nappies usually come with inserts for the pocket (microfibre being the most common) however you can experiment with absorbency by using a variety of different inserts depending on your requirements. Bamboo or organic cotton are usually more absorbent than microfibre, however microfibre absorbs quicker so if you require extra absorbency a combination of microfibre insert with bamboo/hemp/cotton underneath is usually a good idea.