Jujitsu is a broad term used to represent a style of Martial Arts that originated from the samurai and was one of the key forms they practiced for hand-to-hand combat. From this art derives many of the modern styles, such as Judo and Aikido. It is sometimes lumped into the even wider term of “karate,” though that does it a great injustice as the art is quite different in origin and intent.
The word Jujitsu, sometimes also spelled Jiu-Jitsu, Jujutsu, is literally translated to "the gentle art." Its origins are clouded by several legends, some saying it came from a Chinese emigrant, some that it is indigenous to Japan. Regardless of the origins, the idea behind Jujitsu is to maintain efficient use of energy, minimal movements, and utilizing your opponent's momentum to your advantage. A similar philosophy can be seen in other "internal" or softer styles. However, when performed, there is no mistaking the external power of Jujitsu.
Traditional Jujitsu does incorporate some weapons, such as the katana, spears and other weapons that would have been common to the samurai. As with many styles though, it is rare for a lower rank student to work weapons and few schools actually teach this aspect of the art. In fact, some schools break from tradition an incorporate weapons and forms from styles other than Jujitsu just to provide a weapons component to their students.
Jujitsu focuses on immobilization and taking the opponent down to the floor. So it is common to see the opponent either locked in a painful position or thrown at the end of a movement. Other Japanese styles, such as kenpo, tend to focus more on strikes to deliver a final deadly blow and then stepping away. Jujitsu will instead lock the opponent down and not release him or her until the Martial Artist chooses.
Because of this concept of immobilizing the opponent, Jujitsu is often practiced by law enforcement groups and has been compared at times to wrestling and several more Western means of hand-to-hand combat.