Unlike some other social media platforms, Mastodon has not one timeline, but three. They are broken down as follows:
The Home timeline show posts and boosts from users and hashtags you have chosen to follow. This is an important distinction from other platforms; Mastodon is not algorithm driven so this timeline will remain empty until you choose what to fill it with. On Mastodon you are your algorithm, so don't be afraid to follow other users and hashtags if they look interesting. You can always prune your follows later.
“Treat your timeline like a bonsai tree, growing it and pruning it regularly” - Anon Mastodon User
The Local timeline shows posts from all users on your local instance ( e.g. other users from friendsofdesoto.social if you are on this instance). This will include anyone on the server whose posts are set to anything but private visibility
The Federated timeline is a collection of all posts and a boosts your local server has collected from across the Fediverse. It is not the same as a fire hose of all Fediverse activity, but it will include posts from any other servers that your local instance had Federated, or communicated with. These posts are often less relevant to your interest's, but can be helpful in discovering new content.
“Help! I've followed to many random people and now I can't make sense of my timeline” - You presumably
Good News, Mastodon gives you the tools to break up your timeline. You can create custom lists. Lists can contain users that you follow, and can be viewed like their own separate timelines.
To create a custom list select Lists from the right column of the Mastodon Web interface, the click Add list at the top.
Once the list is created, open it and click the Settings button to add users.
You can also configure reply visibility meaning that replies to posts you make in these lists can be set to only be share with other users in the list, or shared with your entire network, as they would be on your home or local timelines.
Custom Lists are a helpful way to beak-up what might otherwise be a very chaotic Fediverse and allows you to compartmentalize your timeline without the need to manage multiple separate accounts.