Aikido is a martial art founded by Morihei Ueshiba
in the first half of the 20th century, by gathering together techniques and principles of several old Japanese martial arts.
The principal point that makes Aikido different from other
martial arts is that it does not contain competition; one has only to fight his own limits.
Aikido might be described by using the name it had temporarily in the 1920s: Aiki-jujutsu. This means that it is a martial art ("jutsu") based on relaxation and flexibility ("ju"), that uses the principle of "aiki". About the principle of "aiki" my working definition is "getting a place and a posture so that the attacker cannot do any harm, while myself I am able to work on my attacker."
The forms and techniques to use the "aiki" principle and also the "ju" principle are thoroughly shown and explained in detail from the beginning of the first day in a dojo. Getting from the beginning to project a partner well-trained to hit is not necessarily easy nor fast, but still in aikido, we keep practicing aikido techniques, trying to master them and also to understand the meaning put into them by the Founder.
Once an aikidoka got a certain level, the movements of the projecting partner (tori) harmonize so well with those of the attacking partner, that a person looking from outside may think that uke voluntarily lets himself leaded through the technique. Also,as it IS always possible that uke voluntarily lets himself leaded by a partner who could not do really the technique, the fact is that is very hard for the beholder to distinguish between a master technique from one of an usual aikidoka practicing with a docile partner.
Once that in aikido there is no competition, there are left only two
ways to do aikido: one is to practice its forms (keiko) and the other to demonstrate one's acquired techniques to others (embu).