Fwiw, if you don't know here's a (quite simplified, there's filters/blocks/moderation considerations also) run-down what your Mastodon timelines show:
Home: posts from people you follow (from any instance)
Local: public posts from all people on your instance
Federated: public posts from all people on your instance and all other instances it is exchanging data with*
*basically when someone on your instance follows someone on another instance or vice versa they "count" for federated timelines