[Mikey Zoppo]

The answer to your questions would take quite some time to write. You should do a little googling about the differences as there are many articles.

But if you’re going to get started with AE, I’d recommend Andrew Kramers basic training series (https://www.videocopilot.net/basic/). It’s going to provide a very BASIC overview of all the core components of After Effects. These tutorials were recorded many years ago so the version of AE he’s using is much older. But most of it will still apply. It’s enough to get you understanding what AE is capable of, how it works, and the various ways to use it.