It's a token for advertisement that rewards the user, to be used at Brave browser: https://brave.com https://github.com/brave
People switched to Chrome because Google told you it was a better experience every time you made a search. I don't see how people of my parents generation (60s) will ever hear about Brave.
Do your parents like paying half their data plan ($23/month in the US) to load tracking scripts and ads? See https://medium.com/@robleathern/carriers-are-making-more-fro.... Brave is 3-7x faster on top news/media sites than Chrome on Android.
All this and more is discussed at https://basicattentiontoken.org/.
How do small faster browsers get big? Marketing. To counter, big browsers have to block by default and none will (Apple comes closest and is our best ally). They're all beholden.