We use the word "debonair" to describe men (in real life and in fiction) who are strong and self-assured, who carry themselves with pride and self-possession, and who know how to dress exceptionally well. In the gif above, you can see the debonair dancer, Fred Astaire, on the left, and his stunning partner, Ginger Rogers, on the right. (Notice how I called Fred debonair, but not Ginger. Even though Ginger is indisputably cool, confident, and good-looking, we don't apply the word "debonair" to women. It's a masculine word.)
Sometimes, we talk about debonair clothes or debonair manners, but usually we talk about debonair men. Pictured below is Idris Elba, a debonair fellow who often plays debonair characters in movies.