In baseball, an "earned run" is a run that scores as a result of a team's offensive play without the benefit of an error or a passed ball. This means that the run is attributed to the skill of the batters and not due to mistakes made by the defensive team. Earned runs are important for evaluating a pitcher's performance, as they reflect how well the pitcher can prevent scoring. To calculate earned runs, the official scorer considers the number of runs that score while the pitcher is on the mound, excluding any runs that result from errors. This statistic helps teams and fans understand a pitcher's effectiveness, as it distinguishes between runs that are earned through legitimate hits and those that are unearned due to defensive blunders.