On May 5, 1862, the Mexican army defeated the French army at the Battle of Puebla. This single military battle signified defeat of a European colonial power and a victory for the Mexican people. This battle was the root of Cinco de Mayo.
Cinco de Mayo is not the celebration of Mexican Independence, which is celebrated on September 16th. It has come to be about much more than one battle in the colonial history of Mexico. Rather, it has come to signify Hispanic and Mexican pride and a time to celebrate the rich culture.
It is a time of song, dance, partying and a time to be proud to be of Hispanic descent. And to drink lots of tequila! (from www.cute-calendar.com)