A Designed is something like Captain America, or Khan, or someone who is the product of scientific meddling (as opposed to Augmented, which is more Six Million Dollar Man - cybernetics). A Chosen is a subset of Designed where, instead of science, it's more prophecy/mysticism. Think Buffy, for example. They're basically perfect human beings.
Mutants - well, you can probably figure out what sort of characters those are! It's not full-on superhero, but it allows for characters with special abilities.
Not all campaigns will have all of these, of course. An A-Team style campaign would only have humans. A 007 style campaign might add Augmented into the mix.
