It's more or less a tagging system, but we called it groups because the name 'tag' is not great. So all groups/subreddits already exist but most have no posts. For example:

https://www.peachesnstink.com/r/sports
https://www.peachesnstink.com/r/animals
https://www.peachesnstink.com/r/golf

But of course if you create a new post and assign it to the group 'sports', then it'd show up there.

I always use 'meta' when I update the site so they are all grouped here:

https://www.peachesnstink.com/r/meta

What I'm planning on doing is private groups - where you can take ownership of an empty group and then only allow certain users to access/see posts and comments for that group.