PER stands for Player Efficiency Rating and is a statistic that measures a player's overall efficiency on the court. It takes into account a player's positive contributions (points, rebounds, assists, etc.) and negative contributions (turnovers, missed shots, etc.) and adjusts for pace of play. The formula for PER is (Points + Rebounds + Assists + Steals + Blocks - Missed Shots - Turnovers) / Minutes Played.