No gloves, no rounds, minimal rules. It's as close as it gets to street fighting but with trained MMA fighters. Watch the interview video if your new to Vale Tudo. Fights start around 7pm EST. also there may be a limit on passes to keep the live feed smooth so get one now if your interested.
The organization just started this year by fighters and is still somewhat underground but growing. Here's some info about them Learn About RioHeroes.
It's everything the UFC and other MMA organizations wish they could get away with plus I'm not sure mainstream audiences and athletic commissions are ready for it, as it would be banned real quick like the UFC was when it first started out.