Brazilian Jiu-Jitsu teaches that a smaller, weaker person can successfully defend against a bigger, stronger assailant by using leverage and proper technique. Among the most common techniques are joint locks (i.e., arm bar, Kimura, paint brush, elbow lock) and choke holds (i.e., rear naked choke, baseball bat choke, clock choke, triangle choke). A choke is considered any technique for either blocking the airway or stopping the bloodflow of the corotid arteries which carry blood to the brain.
Royce Gracie is creddited for giving Brazilian Jiu-Jitsu world recognition by bringing it to the UFC in the 1990's. Gracie Jiu-Jitsu is a very specific derivitive of Brazilian Jiu-Jitsu which encompasses an entire lifestyle of philosophy, diet, training, and brotherhood.