I don’t know if the Fediverse needs much introduction, especially in these circles, but in case you don’t know what it is, it’s a open network of servers that implement various kind of social- and social-like networks. Most things are related to ActivityPub, that has been implemented by various Server implementations, such as Mastodon, Pleroma (Twitter-likes), PeerTube (YouTube-like), WriteFreely (federated blog), etc. The joke is that these platforms should ideally all interoperate, making it, among other things, easy for content to freely spread beyond one medium.
I’d suggest posting the links like this:
as to make it easy to copy the user handle, but as also not to confuse it with an email address.