Sorry Heidi and any other lost soul,
Carnival - The word Carnival is sometimes used interchangeably with Mardi Gras, but that isn't correct. The Carnival (a Latin term that translates into farewell to the flesh) season begins on the Feast of the Epiphany (January 6) or Twelfth Night as in the twelve days of Christmas and culminates on Mardi Gras (French for Fat Tuesday). Mardi Gras is only one day. The season can last up to two months. It just depends on when Ash Wednesday falls.
A Krewe (Old English spelling of crew) is a Carnival organization. The membership roster varies by organization - all male, all female or both. How to join? Most are by invitation only and don't worry if they want you, they come to you. It is a major NO-NO to ask. There are more open Krewes who aren't as strict as all that.
King, Queen, Maid, Duchess - Depending on the organization, they may or may not have these. Carnival is about pretend and many pretend to be royalty for a day. It is a high honor to be selected.
Debutante - A young woman who is being presented to society. Some consider it a throw back to when fathers were saying hey my daughter is available, but again it is a high honor to be selected. Some Krewes have only debs but sometimes a Duchess or maid can be a deb. It just depends on the club.
Ball - Just what it means, a fancy party. Most Krewes have a only a ball.
Tableau - An organized skit or performance that carries out the theme of the ball.
www.mglinks.com is a helpful tool.