Champion primarily refers to a winner, someone who takes first place or first prize in a competition. For example, a tennis champion is the person who wins the tournament.
The term also describes someone who demonstrates clear superiority in a specific skill or field. For instance, a champion at selling would be a person who excels at making sales.
"A winner of first prize or first place in competition; a tennis champion; also: one who shows marked superiority; a champion at selling."
The word "champion" covers both literal and figurative excellence, either through competitive victory or exceptional performance in a particular area.