There are two kinds of kumite, "yakosuko" or pre-arranged, and "jiyu" or free, not pre-arranged sparring.
The goal of both exercises is for practitioners to learn distancing, control, application of explosive technique, and flow. Kumite in the dojo is not akin to an actual fight because the goal of both people in the dojo is the improvement of the other, whereas the goal of an actual fight is either to harm or to survive and escape.
Kumite is taught based on the needs and abilities of each person. Power, speed, and the level of contact increase based on individual development.
Okikukai Shohei-ryu Yakusoku-Kumite by MATSUSHIMA Yoshiharu & SEIKEN Nashiro. Recorded in Serbia at September 2007.
Uechi-ryu Dan Yakusoku-Kumite by Kyuna Asakyo and Tobaru Keicho. Okinawa, 10th October 1981
Sensei Ken Nakamatsu showing various training techniques for sparring.