Muting and blocking are really important tools on Mastodon. Mutes hide someone from you without them knowing, whereas blocks totally cut off contact with an account and prevent interactions.
To mute or block someone, go to one of their posts or their profile page and click ⋯, then select "Mute" or "Block".
I've done a guide all about mutes and blocks on Mastodon which answers lots of questions:
➡️ https://fedi.tips/blocking-and-muting-on-the-fediverse
If I've missed something, let me know! 🙂