A Batted Ball Event represents any batted ball that produces a result. This includes outs, hits and errors. Any fair ball is a Batted Ball Event. So, too, are foul balls that result in an out or an error.
Batted Ball Events are a fundamental part of Statcast data. They are used as the denominator when determining batting metrics such as average Exit Velocity and average Launch Angle. All Batted Ball Events by a given hitter are used to determine these averages.