Charley is Willy's longtime neighbor who is just plain nice. He functions as a voice of reason and practicality in a world of delusion and confusion. Charley is humble, reserved, down to earth, and honest. Since he actually has some self-confidence, unlike Willy, Charley doesn't need to brag to everyone to make himself feel better. At one point in the play, Willy is shocked to find that Charley hasn't shouted from the rooftops the fact that his son, Bernard, is arguing a case before the Supreme Court.
Charley is the character against whom Willy is always measuring himself. Willy constantly criticizes Charley for not being well-liked, for not being interested in football, for having a nerdy son, and for not being a real man. It seems like Willy is always putting his neighbor down because he's jealous of him, plain and simple.
Willy can't understand why Charley is successful in business and in parenting. Even more frustrating to Willy, Charley is generous and helpful, offering him advice, money, and even a job. This, of course, tells us more about our main character; by refusing his neighbor's help, Willy shows his pride and tendency for self-destruction.