It's like Twitter, but federated, like e-mail and Matrix.
Manjaro should have an official account on a Mastodon instance. Currently only commercial platforms are available (Twitter, Facebook). A Mastodon account would also give the Manjaro users a bit more insight into the open source universe (many people don't know about Mastodon).
Manjaro ARM does at least have an official account.
Manjaro is also represented, but with a crossposter bot account via Twitter.
There should be a link to it, next to the GitLab, Twitter, YouTube, Facebook links on the homepage.