Fitteds

Fitted cloth diapers are called "fitted" because unlike their predecessors, prefolds, they are fitted to the baby's shape with elastic waist and legs and they (usually) have a snap or velcro closure.  (Some have no closure built in and are meant to be used with a Snappi or pin.)  They are not waterproof so you have to use a separate cover.  This keeps the cost down while allowing you to customize your diapering system to suit your baby's needs.  Fitteds are especially popular for nighttime diapering.