Base runners play a fundamental role in the offensive side of softball. To win softball games, a team must score runs. To score runs, players must find a way to get on base, then move from base to base to get closer to and reach home plate to tally a run. Runs are precious in softball because, in order to win, a team must outscore one another. When runners get on base, a bunt, ground ball, or fly ball can move the runner safely to the next base depending on the number of outs.
Tagging up occurs in softball when a runner or runners on base advance to the next base on a ball hit in the air, often to the outfield, with less than two outs. The runner must be in contact with the base they started at and wait until the ball is caught, before advancing to the next base. If a runner leaves the base early, and the defensive team throws the ball back to the base the runner started at, the call is up to the umpire.