The holiday of Cinco De Mayo, The 5th Of May, commemorates the victory of the Mexican militia over the French army at The Battle Of Puebla in 1862. It is primarily a regional holiday celebrated in the Mexican state capital city of Puebla and throughout the state of Puebla, with some recognition in other parts of the Mexico, and especially in U.S. cities with a significant Mexican population. It is not, as many people think, Mexico's Independence Day, which is actually September 16.
I think we should all celebrate with Margaritas and tortillas. It works for me!