Aikido, translated to "the way of divine harmony", is a Japanese soft martial art and philosophy that was developed by Morihei Ueshiba and officially named in 1942. It is technically based off of various forms of jujutsu, especially daitoryu-jujutsu. Aikido is also a very spiritual martial art based on Omotokyo and the belief in ki.

Aikido doesn't have an exact structure that everyone follows. The ethical, meta-physical, and philosophical beliefs are vague and different for each practitioner, but for the most part they follow similar beliefs.

Aikido is not used for fighting, but instead self-defense to try to resolve conflict with as little violence as possible. It doesn't use strikes or kicks, but instead holds, grappling, throws, and some weapons to use an opponent's strength against them. Most of the movements in aikido are circular.

The main goal of aikido is to create harmony and improvement between all people and the universe itself. Most schools of aikido feel that competition is unacceptable as competition goes against the belief of harmony.

Links - An informative aikido site.