Every year, more than 4 million people come from around the world to be part of what is often billed as the "greatest free party on Earth" -- Mardi Gras!

Mardi Gras, also called Carnival in some countries, is celebrated around the world. We're going to focus here on the festivities in New Orleans, Louisiana.

Beginning in January, the city of New Orleans starts a variety of festivities that culminate with Mardi Gras Day, or Fat Tuesday -- the day before Ash Wednesday and Lent. For about two weeks before Fat Tuesday, residents and visitors alike enjoy dozens of parades with wildly imaginative floats bearing outrageously costumed party-goers tossing colored beads into the screaming crowds. The parties continue into the night as revelers seek out distinctive "Nawlins" jazz and blues as well as Cajun and Creole food.

Many of us have heard of New Orleans' famous Bourbon Street and French Quarter, but many of us have no idea what Mardi Gras celebrates or why it's held when it is. And what's with the plastic beads tossed from floats to bystanders? King Cake, Boeuf Gras, doubloons -- what are these about? In this edition of HowStuffWorks, we'll take a closer look at Mardi Gras, its origins and traditions. And we'll look at some ways to have Mardi Gras celebrations both in New Orleans and at home!