True Shooting Percentage; the formula is PTS / (2 * (FGA + 0.44 * FTA)). True shooting percentage is a measure of shooting efficiency that takes into account field goals, 3-point field goals, and free throws.
Effective Field Goal Percentage; the formula is (FG + 0.5 * 3P) / FGA. This statistic adjusts for the fact that a 3-point field goal is worth one more point than a 2-point field goal.
For example, suppose Player A goes 4 for 10 with 2 threes, while Player B goes 5 for 10 with 0 threes. Each player would have 10 points from field goals, and thus would have the same effective field goal percentage (50%).
Offensive Rebound Percentage (available since the 1970-71 season in the NBA); the formula is 100 * (ORB * (Tm MP / 5)) / (MP * (Tm ORB + Opp DRB)). Offensive rebound percentage is an estimate of the percentage of available offensive rebounds a player grabbed while he was on the floor.