True Earned Run Average, like FIP, attempts to quantify a pitcher's performance based on what he can control. But unlike FIP -- which factors only home runs, strikeouts, walks and HBPs -- tERA also accounts for batted-ball tendencies. That means pitchers who record mostly ground balls and popups, as opposed to line drives and fly balls, are rewarded for inducing weaker contact.
For example, if a pitcher has a high FIP but has also gotten a lot of weak contact on balls put in play, his tERA will be lower than his FIP.
tERA is meant to be a more accurate indicator of a pitcher's performance than ERA. Even though most fantasy leagues count ERA, tERA can help assess a pitcher's talent and predict future success.