Brazilian Jiu Jitsu (BJJ) is a grappling based martial art that centres itself on the skill of controlling a resisting opponent in such a way that it often forces them to submit. BJJ is one of the fastest growing combat sports in the world alongside MMA. BJJ promotes the idea that a smaller and weaker person can defend against and defeat bigger stronger opponents using leverage and technique.  BJJ heroes has a great write up on BJJ if you have another spare minute –