One of the nicest community features on medium and small servers is the Local timeline, which shows all public posts by people on that server.
You can see this on Mastodon's website interface by clicking "Local", or on the official Mastodon app by clicking the magnifying glass 🔍 and then "Community".
If you want to see the Local timeline of other servers, you can usually go to their website and click "Local". Also some apps support viewing them, such as Fedilab, Subway Tooter and Ice Cubes.
