What is an unearned run?

An unearned run is a run that is scored due to an error made by the opposing team, rather than through a successful play on the part of the batting team. For example, if a fielder drops a ball that should have been an out, and a runner scores as a result, that run would be considered unearned. Unearned runs do not count towards a pitcher's earned run average (ERA), which is a statistic used to measure a pitcher's performance. Unearned runs can sometimes be controversial, as they are not necessarily indicative of the actual skill or ability of the team that scores them.