An AIO, or All-In-One, is exactly what it sounds like. These cloth diapers are the easiest and most leakproof diapers to use and have a built-in diaper cover sewn into the cotton or fleece layer. They fasten with snaps or velcro and work like the ease of a disposable. NO diaper cover required. The cover and absorbent inner is attached as one unit. It is a type of diaper that functions completely on its own without the need for extra accessories. It does not require separate soaker material to absorb nor a separate diaper cover to contain leaks. All of the features are neatly packaged into one diaper. Many parents find this type of diaper to be the height of convenience since all they need is in one place. It also saves on space when traveling.