Brazilian Jiu-Jitsu is a martial art as well as combat sport. BJJ is an extremely effective form of self-defense that focuses on grappling, especially ground fighting.
It promotes the principle that a smaller, weaker person can successfully defend himself against a bigger, stronger assailant using leverage and proper technique notably by applying joint-locks and chokeholds to defeat the other person.
Jiu Jitsu can be trained for sport grappling tournaments (gi and no-gi) and mixed martial arts (MMA) competition or self-defense.
Sparring (commonly referred to as 'rolling') plays a major role in training.