AIO diapers are most similar to disposables. Most AIOs come in one piece and have the inserts and cover either sewed together, or have buttons where you can snap the inserts onto the diaper (the reason being that it lets you change the absorbency of the diaper and/or helps the diaper to dry faster). The one piece means that you can throw the entire nappy in the wet bag/diaper bin when it's dirty.
AI2s are sometime called hybrid diapers, and come with absorbent inserts that you can usually attach to the diaper cover with a snap button that helps the inserts to stay in place. The diaper covers are usually unlined, so that you can reuse the covers several times during the day (usually if baby only pees on the insert). Some brands of AI2 diapers also sell disposable soaker pads, which is why it's sometimes referred to as a "hybrid diaper" since it's both disposable and reusable.
Are squared cloth usually made of cotton, or an absorbent cotton-blend fabric that's very similar to the traditional cotton cloth flat fabrics widely used in the past. With prefolds, however, the cloth is usually divided into three parts (three rectangles) with the middle part having more layers of absorbency. While you can pin larger prefolds onto baby, usually, folding it in three parts (hence why it's also known as trifolds) to make a rectangle is sufficient to create a very absorbent insert for your favorite diaper cover or pocket diaper.
Are made of only absorbent cloth and look similar to an AIO diaper without the waterproof cover. Fitted diapers are created with a contoured shape, snap or hook-and-loop closures, and elastics around the legs to contain messes. You'll need a waterproof diaper cover to go over it.
Have a pocket opening either in the back, front or middle of the diaper where you can stuff an absorbent insert. Some pocket diapers come with specifically design inserts, but most allow you to use any and as many inserts you wish as long as it fits inside the pocket opening without bunching up.