Brave works by blocking outside online ads and ad tracking to speed up performance, rather than requiring an add-on ad blocker or other privacy protectors. The beta, released last week, is available on Windows and OS X on the desktop, with iOS and Android versions to come.
Eich has outlined his philosophy, which I won't rehash since Gregg Keizer did a fine job in his article covering the announcement. I would only add that I like the notion of blocking outside ads because that's where malware is coming from, as Forbes recently learned the hard way. Brave scrubs websites of most of their ads and all tracking, and replaces those ads with its own. Hopefully Brave will do a better job monitoring its ads for malware than some of the ad delivery networks have done.
Rather than reinvent the wheel, Eich and his new company built the browser on Chromium, the open source browser from Google on which Chrome is built. This raised a few eyebrows and was seen as a middle finger at Mozilla over its treatment of Eich, but he denies it.