I'm glad this community is here because I feel very stupid. I've seen videos likening the fediverse to email and phone networks. Some of what I've seen implies that not only are lemmy instances connected but lemmy instances can also be connected with mastodon, peertube, and others. Is this true? How to I connect to other instances or even other platforms?
You are registered on a Lemmy instance and from those you can only follow communities (that are structured the way Lemmy communities are, but the backend doesn't need to actually be Lemmy), not people. Mastodon, PeerTube etc. are places where people post to their own profiles, so you can't follow those from Lemmy, you need to create an account on e.g. Mastodon to do that. You can combine both worlds with some backends (piefed, mbin, friendica).