Complex sentence: Football officials are commonly referred to as referees, but each position has specific duties and a specific name: referee, umpire, head linesman, line judge, back judge, side judge, and field judge.
Split into simpler sentences: Football officials are commonly referred to as referees, but each has a title based on his position. They consist of: referee, head linesman, line judge, umpire, back judge, side judge, and field judge.