You have several timelines to browse trough
- Timeline aka Home Timeline - this timeline contains all posts by people you follow and your own posts, as well as posts mentioning you directly.
- Bookmarks all the posts you've bookmarked. You can bookmark a post by clicking the three dots on the bottom right of the post and choose Bookmark.
- Direct Messages all posts with
directscope addressed to you or mentioning you.
- Public Timelines all public posts made by users on the instance you're on
- The Whole Known Network also known as TWKN or Federated Timeline - all public posts known by your instance. Due to nature of the network your instance may not know all the posts on the network, so only posts known by your instance are shown there.
Note that by default you will see all posts made by other users on your Home Timeline, this contrast behavior of Twitter and Mastodon, which shows you only non-reply posts and replies to people you follow. You can change said behavior in the settings.
By default instances will try to send activities (e.g. posts, favorites, etc.) up to 7 days or until the target server received them. For this reason posts that are up to 7 days old and your server didn't know about yet can pop up on your timeline. This is the default behaviour and can be changed by your admin.