Aikido (the way of the harmonious spirit) was developed by Morihei Ueshiba in the 1920's. It is derived from Daito-Ryu Aiki-jujutsu. Ueshiba Sensei wanted an art that practitioners could use to defend themselves but at the same time protect the attackers from injury if possible.
Aikido techniques are primarily defensive. Aikido practitioners use an opponent's energy to redirect an attack and unbalance them. A throw or joint lock are added to terminate the attack. Properly executed techniques don't require strength, making Aikido good for all ages and body types.
Aikido training incorporates both physical and mental aspects. Beginners learn first how to safely fall and roll. Training in Aikido includes open hand techniques, throws, joint locks, and pins as well as weapons training with the sword, short staff, and knife.