Answer and Explanation:
In literature, a foil is a character that exhibits behaviors and traits that contrast with those of another character. In "Pride and Prejudice", Jane Austen uses Mr. Bingley as a foil character, since he opposes Mr. Darcy's traits.
Austen brilliantly makes the two men the best of friends despite - or maybe because of - their differences. To illustrate Darcy's arrogance and pride, Austen places the two in situations where they act in totally different ways. For instance, at the public ball they attend, Bingley makes a point of meeting as many people as possible, and he dances with several young ladies throughout the party. Darcy, on the other hand, barely speaks to anyone outside his own group, and chooses to not dance at all. While Bingley finds the girls attractive, Darcy sees nothing special in any of them.
The characters in the novel themselves can't help but marvel at the difference between the two men. And the more Bingley shines, the more Darcy is regarded as boring and proud. All that helps build the misunderstandings that will unravel the plot.