It is an Israeli fighting style (whose name means "close combat/contact" in Hebrew) designed to teach self-defense techniques in a simple way using the body reflexes.
Krav Maga was founded around the 40s by Imi Lichtenfeld, based on his street fights experiences in Bratislava in the 30s.
It was not the first martial art used by jewish defense groups - another method called Kapap was already in use. However, Imi wanted a fighting style enabling the learning of self defense in the shortest possible time.
Until 1964 the teaching of Krav Maga was restricted to the military elite. From this date, it was released to the general population. Since 1980 on, it has been taught outside the state of Israel.
As all blows are allowed, there are no rules or competitions.