I see what a prefold is...but how do I fold it?

It's not as complicated as you may think! The easiest way to use a prefold is fold longways in thirds and lay it in the cover. There are more ways to fold, check the links below, and you can use pins or a Snappi, or just fasten the cover.

SNAPPI tutorial - Never use a pin again!

What's the difference between different kinds of prefolds?

Personal preference, really. Some think Indians or Europeans are softer, while Chinese absorb more. There are also hemp or bamboo.