. Usually a round is 5 minutes. After the first 5 minutes the first round is over. and the fighters go to their corners for a short break than the fight resumes for another 5 minutes. then another break then the final round which is another 5 minutes after the final round the judges score the fight and decide who win. But a round could end any time due to a knockout, or submission which is when someone taps, or injury.
normally they are just timed rounds, the rules are the main focus . some rules are no kicking a down opponent in the head , soccor kicks, elbows , hits to the back of the head and other stuff. normally 5min per round or longer maybe shorter.