This is a play in which a runner loses his right to be on a base by reason of the batter becoming a runner. Lets look at an example there is a man on first, one out, and the ball is hit to first baseman who touches the bag and the batter / runner is out. The force is removed at that moment and the runner advancing to second must be tagged to get him out. If the first baseman was far enough away from first base and threw the ball to second base, the runner going from first to second would be forced out at second and no tag would be required. A double play involves a force play at second base.