Most people use a liner in between the nappy and the child's skin. The advantage of this is to reduce staining from poo (only really effective after solids have been introduced) and to make it easier to remove the poo before washing. They can also help keep the skin dry, however, babies don't usually mind being wet (they do mind being dirty) and it does not cause problems for nappy rash so do not feel that you HAVE to have them - especially on occasions when you run out.

Fleece liners are excellent. They are soft (even after air drying) next to your baby's skin. An they are yet another thing that to reuse instead of throwing away.