Well, cowboy diplomacy is something like when you watch cowboy movies or shows where the cowboys are tough, brave and always ready to fight for what they want. In real life, this means when people use force or the threat of force to get what they want from other people or countries.
It's like when you tell your friends that you'll beat them up if they don't let you play with their toy. This is not very nice, and it's not a good way to make friends. But some people think that using strong, tough tactics is the best way to get things done.
Cowboy diplomacy can be dangerous because it can lead countries to go to war with each other, and wars can hurt a lot of people. Instead, it's better to talk things out and try to find peaceful solutions to problems.