There is no single site or app that is "Mastodon." This isn't like Twitter, or Facebook.

Mastodon.social isn't "Mastodon" anymore than Gmail is "email." Gmail is one very popular email server, Mastodon.social is one very popular #Mastodon server.

Same goes for mastodon.online, mstdn.social, mas.to, etc.

This seems to be tripping up a lot of new people during the #twittermigration to the #fediverse

#FediTips

Why does this matter? Because if you only share your @username with others, no one can find you. You have to include your instance as well.
@mike ah but what if i dont want anyone to find me :)