The term 'play caller' is used to describe a variety of roles in sports. An UMP, or umpire, is an official who enforces the rules of a game and makes sure that it is played fairly. A COACH is a person who trains and guides a team, helping them to develop their skills and strategies. A QUARTERBACK is a player in American football who directs the offense on the field and calls the plays. Finally, a REF, or referee, is an official who oversees a game and makes sure that it is played according to the rules. All of these roles are important in ensuring that a game is played fairly and safely.