Hi! Welcome! AIOs and Pockets are a good place to start because they are so much like disp. diapers. AIOs are the cover and the "diaper" material all sewn together. Pockets are a cover with a layer of microfleece sewn in the inside to form a pocket that you'll need to stuff with some sort of absorbant material. Contours, fitteds and prefolds all need a cover to be waterproof. Fitteds have snap or velcro closures...contours and prefolds can be placed in a cover that snaps or velcros (or they can be pinned or snappied shut before going in a cover). HTHs!