Question

What's a character foil?

Answer 1

A foil is a character who contrasts with another character, usually the protagonist, and, in so doing, highlights various facets of the main character's personality. A foil has some important characteristics in common with the other character, such as, frequently, superficial traits or personal history. The author may use the foil to throw the character of the protagonist into sharper relief.

Answer 2

Foil characters usually contrast the protagonist.

By contasting two personality traits, it ususally brings one out.

Take a thin person, and a fat person. The fat person looks fatter against a skinny person. They look normal in a crowd of overweight people.