Most SE sites have a Meta section of the site where you ask questions about the site itself. Is Area51 Discussions like a Meta site?
Yes, it should have been called Area51.meta. It's the same thing.
Back in our earliest days, we sometimes had a bad habit of relabeling common "features" found around the Internet to something else because we implemented them just a bit differently.
For example, the "help" or "support" on our Q&A sites became "meta". It fit and people became used to it… but when Area 51 became something just a bit different, we changed "meta" to "discussion" because it just wasn't quite the same (even though it essentally… is).
It's too much trouble to change it now.