Mardi Gras season begins on the 12th day of Christmas - January 6, but the final day of partying is always 47 days before Easter, on the day before the start of Lent, or Ash Wednesday. This famous and ancient holiday is also known as "Fat Tuesday." On Fat Tuesday, Christians end their partying and begin a 46 day fast that lasts until Easter. In Europe and other nations around the world, the season is also known as Carnival (Carnivale, Karneval).
In New Orleans, Lousiana (USA) the most famous of Mardi Gras celebrations takes place every year - with parties, festivities, and parades that push the limits of propriety on everything from food and drink to attire and frivolity. In Pennsylvania-German culture, Fat Tuesday is the day to eat many many "FastNachts" - special Fast Night potato doughnuts without holes - in preparation for Lent when foods are typically given up until Easter. Fastnacht Day is a day to feast on doughnuts. Pennsylvania Germans used up the fat and sugar they had on hand before the Lenten fast by making these yeast-raised potato doughnuts and eating them with syrup.
Read more about the history of Fastnacht/Karneval.
Mardi Gras celebrants party in costume - masquerade balls and parades are a major part of the holiday - wearing traditional/offical Mardi Gras colors of purple, green, and gold, to represent justice, faith, and power respectively. Bead necklaces, feathers, and shiny fabrics are hallmarks of Mardi Gras holiday costumes.