Aikido is a Japanese martial art developed by Morihei Ueshiba (often referred to by his title 'O Sensei' or 'Great Teacher'). On a purely physical level it is an art involving some throws and joint locks that are derived from Jujitsu and some throws and other techniques derived from Kenjutsu. Aikido focuses not on punching or kicking opponents, but rather on using their own energy to gain control of them or to throw them away from you. It is not a static art, but places great emphasis on motion and the dynamics of movement.
Upon closer examination, practitioners will find from Aikido what they are looking for, whether it is applicable self-defense technique, spiritual enlightenment, physical health or peace of mind. O Sensei emphasized the moral and spiritual aspects of this art, placing great weight on the development of harmony and peace. "The Way of Harmony of the Spirit" is one way that "Aikido" may be translated into English. This is still true of Aikido today, although different styles emphasize the more spiritual aspects to greater or lesser degrees. Although the idea of a martial discipline striving for peace and harmony may seem paradoxical, it is the most basic tenet of the art.
Reference: https://www.aikidofaq.com/introduction.html
Sometimes refered to as "Sport Aikido", Tomiki style differs from the other schools of Aikido by having competitive tournaments as a method to test ones ability and the effectiveness of techniques. It is not compulsory to take part in competition however as it represents only a part of overall training.
Competition usually consists of bouts where the participants take turns to attack the other with a soft tanto (knife). The defender attempts to avoid the strikes and score points by throwing the attacker.
Tomiki Aikido consists of soft and flowing techniques and is therefore suitable and effective for both men and women of all levels of fitness.
Reference: http://www.jugokan.com/tomiki-style
Kenji Tomiki (1900 - 1979) was a direct student of both Morihei Ueshiba the originator of Aikido and Jigaro Kano the originator of Judo. He attained the level of 8th Dan in Judo and was the first to be awarded 8th Dan in Aikido in 1942.
He used his knowledge of Judo to introduce to Aikido a system of Katas (set movements), and also competitive Aikido, both as learning tools. Training methods have evolved from its traditional origins but the principles involved have been kept the same.
"I introduced Randori Aikido so that students could make their techniques more effective by 'free play'. These techniques originate from Kata and can develop through Randori to competition. In order to teach the spirit of Budo in a modern educational system, it is necessary to introduce it as a sport.
The reason I developed Randori Aikido from Kata Aikido is because I wished to follow the method and thinking of Dr. Jigaro Kano in which he evolved Judo from old style Ju-jitsu. Dr. Jigaro Kano was one of my greatest teachers. He introduced and established Judo Randori-Ho from ancient Ju-jitsu techniques and styles, for example Tenti or Shino Ryu and Kito Ryu, thereby introducing old style Ju-jitsu into the modern educational system, which enabled it to become the competitive sport it is today, allowing considerable improvement of technical detail by practical application, particularly with respect to throwing techniques and ground work.
In the course of this development it was necessary to leave out much of the Atemi-waza (striking techniques) and Kansetu-waza (Bending or twisting of the joints) which were used very effectively by unarmed practitioners against an armed opponent. But it is my hope that these techniques can be preserved and developed as an independant sport. Hence 'Randori Aikido'."
Reference: http://www.jugokan.com/tomiki-style