Bjj is a grappling art that descended from the Japanese martial art of ju jutsu.
Japanese immigrants brought ju jutsu with them to Brazil in the early 1900s. There, the art was adapted (most notably by the Gracie family) as a form of self-defense in which a smaller person uses technique and leverage to control a larger, stronger opponent.
Modern day Brazilian jiu jitsu has become wildly popular both as a means of self-defense and as a sport.Jiu jitsu is also a favorite with law enforcement officers. Bjj has been proven to drastically reduce injuries to both law enforcement and the people they physically interact with.