Mardi Gras (French for Fat Tuesday) takes place on the Tuesday (Shrove Tuesday) before Ash Wednesday and is an event held by Cajun communities of south Louisiana. It’s part of the Carnival celebration that culminates on Fat Tuesday. In many areas, the term “Mardi Gras” has come to mean the whole period of activity related to the celebratory events, beyond just the single day.
Popular practices on Mardi Gras include wearing masks and costumes, overturning social conventions, dancing, sports competitions, parades, debauchery, etc. Similar expressions to Mardi Gras appear in other European languages sharing the Christian tradition, as it is associated with the religious requirement for confession before Lent begins.
In New Orleans, the festival season stretches the entire period from Twelfth Night (the last night of Christmas which begins on Epiphany) to Ash Wednesday. Others treat the final three-day period before Ash Wednesday as the Mardi Gras. In earlier times, parades were held on New Year’s Day. Other cities famous for Mardi Gras celebrations include Rio de Janeiro, Trinidad and Tobago, Quebec City, Mazatlan and Sinaloa, Mexico. (from Wikipedia and www.cute-calendar.com)