Any illegal contact commited by a player while his team has possession of the ball. The player is charged a personal foul, and the team loses possession; however, the foul does not count as a team foul.
Some examples of offensive fouls are charging, illegal screen and using the non-dribbling hand to push or block a defensive player. The defense has as much right to his established position on the court as the offense does. When the defense gets to a spot first, an offense can't force him out of that spot using contact.