The digital news media outlet AJ+ created a short video that will be useful for you to learn a little bit (and be intrigued to learn more!) of what went down on May 5, 1862 in the Mexican state of Puebla. El Día de la Batalla de Puebla, as it is known in Mexico, involves the French occupation in the Latin American country.
Is it too much to ask that Cinco de Mayo celebrations don't involve wearing big ass sombreros, ponchos, a large mustache, or saying the word "andale" repeatedly? Just saying.
Also, as I am sure this celebration breaks through the barriers of political beliefs and negative sentiment toward immigration reform, a great way to truly celebrate this cultural exchange would be to start treating Mexican and other immigrants from across the border better.