Sorry, I am really new to the idea of the fediverse. So, it is about standartisation for social media protocols so I can interact with users on another side that uses the same standard. Does this mean if I post something on lemmy I can find it on Mastodon, or is it only certain features? I guess I dont understand how this applies to the every day use of there application
It all uses the ActivityPub protocol, so interoperability depends on what end points are used. In this case, favorites on Mastodon and upvotes on Lemmy use the same one as far as I understand it, so they are compatible. If you see a post from a Mastodon user on Lemmy and upvote it, it should translate to a favorite on their end.