It’s based on it yes, but they use different desktop environments. The desktop mint uses is called Cinnamon.

It’s a (better IMO) derivative of Ubuntu, but it uses the Mint desktop environment by default while Ubuntu uses Gnome. To a casual user, most distros are pretty similar other than their defaults. Those defaults aren’t even particularly hard to change. For example, switching mint to Gnome is one command and a couple GUI clicks: https://itsfoss.com/install-gnome-linux-mint/

its a fork of, downstream, tears out a bunch of the annoying shit and has different ux.