@purplewatermelon @valiant Local timeline is the timeline of posts from people on your server.
Federated timeline is the timeline of all the users known to the server you're on -- So everyone that everybody on your local instance is following, and if your server has a "relay" connected to it, which provides a feed of posts from other servers, you'll see those messages as well.
Essentially, the more people your server interacts with, the more you'll see there.
@purplewatermelon local is a timeline for people on the same server as you. Federated is for all instances and is how we found you! I’m on another server entirely :)