MMA, the abbreviation of Mixed Martial Arts, is now one of the most dominant and complete martial arts practiced worldwide. MMA originally emerged from Brazil's Vale Tude and Luta Livre. Sometimes it is also called cage fighting, Freefight or No Holds Barred (NHB) fighting. However, contrary to what is sometimes claimed, there are quite a few regulations in modern MMA and the large organizations and of course not everything is allowed.
The first time the term MMA was used was during what is now widely considered the most important point in modern MMA history, UFC 1 (Ultimate Fighting Championship).
In the 1990s the Gracie family from Brazil brought their adapted (Brazilian) Jiu-Jitsu style to the USA. Ultimately, this resulted in the very first major global MMA tournament: UFC 1.
Originally, the idea was to filter the best fighting styles by allowing pretty much everything. However, MMA has boomed since then and many professional fighters have started cross-training in various fighting styles. To keep it safe and to make the sport more mainstream and therefore commercially accepted, many more rules and weight classes were gradually introduced in what is today a very popular sport and organization: MMA and the UFC.
In fact, MMA is such a big business today worldwide, and especially in the USA, that it competes with the ever-popular professional boxing, pro wrestling and kickboxing.