Comment by nicoburns

I think the easiest way to understand it is this:

Suppose you have a concrete type like

    Vec<i32>

Regular generics enable you to make the contained type generic, so you have:

    Vec<T>

where T can be i32, u32, String, etc. GATs allow you to make the container generic. So you can have:

    T<i32>

where T might be Vec, Option, Box, etc.