You mean this?
It’s the Fediverse logo!
Well, sort of. There’s no central authority on the Fediverse to choose an official logo, but many community members published their own suggestions and one of them has become very widely used. This is probably the nearest the Fediverse will ever get to an official logo.
The creator of the logo released it into the Public Domain, so anyone can use it for any purpose. It’s effectively the flag of the Fediverse, and used to represent it in discussions, videos, apps and lots of other contexts.
The logo’s creator published high quality versions of the logo available to download on Wikimedia Commons ⧉.