Pocket diapers are named for their pocket opening, which needs to be stuffed with an absorbent insert prior to using. Like fitted diapers pocket diapers are "diaper" shaped, have enclosed elastic at the legs and back, and close with either snaps or hook&loop (like Velcro). The difference is that the outside of a pocket diaper is waterproof, so no separate cover is required. Every pocket diaper needs at least one absorbent insert (which is usually included with purchase) to function properly. Some families buy some extra inserts so the pocket diapers can be stuffed with more then one for heavy wetters, naps, or overnights. The trimmest options for inserts are hemp or microterry. You can also use a prefold or flat diaper folded to fit into the pocket diaper for absorbency as well.