Kumite (組手) literally translated means "grappling hands" and is one of the three main sections of karate training, along with kata and kihon. Kumite is the part of karate in which a person trains against an adversary, using the techniques learned from the kihon and kata.
Kumite can be used to develop a particular technique or a skill (e.g. effectively judging and adjusting one's distance from one's opponent) or it can be done in competition.
Depending on Age, Experience and Belt Rank, there are different types of Kumite that may be practiced. Your instructor will advise you on what type of Kumite you will be permitted to train in. Any type of Kumite practice will be permitted on the advice of your instructor and may not be the same for all participants of the same age or rank. It is up to the student to example their skill before the instructor will permit advancement to a new Kumite type.