Waterfox

The first time I've heard about this browser was here on Lemmy maybe 20 minutes ago. A quick look at their webpage says that they use gecko as their web engine, but doesn't specify it bring a fork of Firefox.

To put this in context, most gecko based browsers I've heard about recently have also been Firefox forks. Is Waterfox a Firefox fork? And what does Waterfox do differently that should make people consider it more than Librewolf or another Firefox fork?