A player is charged with a turnover if they lose possession of the ball to the opposing team before a shot is attempted.
There are many actions that can result in a turnover, including: ball stolen by opposing team, throwing a bad pass, throwing the ball out of bounds, stepping out of bounds, committing a double-dribble, palming or traveling violation, committing a backcourt violation, shot clock violation, three-second violation, five-second violation or an offensive foul (charge or illegal screen).