In Mexican culture, a sombrero is a large hat that people use to keep the sun off their foreheads and necks during the workday. The word sombrero means "shady," because the hat provides shade for the person wearing it.
In the United States, sombreros have become representative of Mexicans and Mexico as a whole. This is no doubt partly because of the popular song "The Mexican Hat Dance", also known by its Mexican title "La Cucharacha", which is danced around a sombrero placed on the ground.
Cartoon character Speedy Gonzalez also wears a sombrero.