How do male characters in the play act as a foil for Willy Loman in Death of a Salesman?

A foil is a
character that contrasts with another character in order to emphasize the characteristics that
differ between them.

Willy is insecure, so he acts arrogant, and he is lost,
so he pretends that making money is all there is to life. He spends his time judging himself,
and trying to climb the social ladder.

Charlie, in contrast, is self-assured
and doesn't mind if others don't like him. He is fairly successful in business and content in
his life, although Willy thinks he isn't trying hard enough to achieve success as Willy
envisions it.

These characters are so thoroughly foils to each other that
Willy even develops a grudge against Charlie for being so helpful! Charlie's character
emphasizes the hidden problems that Willy hasthe same problems that eventually destroy him, by
demonstrating what a character without those same problems looks like.