Firefox focus is a simple, lightweight, and private version of Firefox on mobile. Basically it forgets anything you've done once you close the browser, and you can only have 1 tab open.
I use it as my default browser on mobile because I open a lot of links and do a lot of quick research during the day. With a regular browser I end up with dozens of tabs in my library, there's probably 10% that I want to keep and I end up having to delete one by one most of the tabs regularly to do some cleanup.
I'm not sure if that's a use case for a lot of people but I actually use 2 browsers on mobile, one for the things I want to be able to find back later (Orion) and one for the trivial stuff (Firefox Focus).
I have no idea how much work this represents, and how much the FF team has been able to reuse from their original browser, but this is something that I would really like to have!
Thanks for all your work on Orion !