karate is a martial art of Japanese origin that deals with attacks through evasive body movements and/or blocking, and counter attacks using kicks, punches and strikes. Joint locks, restraints and takedowns are also used, but to a lesser extent. People variously practice it as a form of self defense, a way of keeping healthy and a sport.
As a self defense system, karate does not so much teach a set of standard responses to a set of limited scenarios, but rather teaches a set of principles that can be applied in any situation.
As a method of keeping fit and healthy, it develops balance, co-ordination, aerobic fitness, strength and flexibility. In addition, (and unlike many other physical activities), it also challenges the brain and requires constant mental alertness and agility.
Finally, the sporting element allows people of a sporting inclination to test their karate skills against others in a safe and controlled environment.