One question that is asked over and over by the new participants, every year is:

 What is a Krewe?

Well the technically correct answer to that question is

krewe (kr) (pronounced crew)
n. New Orleans , Mardi Gras, Carnival   

Any of several groups with often hereditary* membership whose members organize and participate as costumed participants in the float parades, and balls, in the annual Mardi Gras carnival: example “They . . . watched a parade of bands and New Orleans-style floats run by krewes throwing necklaces of colored beads” (Robert Reinhold).

*Today you can join a krewe without being a hereditary pledge. Some krewes accept applications year around, while others limit membership to certain periods.

Regional Note: In order to organize and stage the enormous Mardi Gras carnival every year, many New Orleans families have belonged for generations to krewes, groups that create elaborate costumes and floats for the many Mardi Gras parades in the three weeks leading up to “Fat Tuesday.” Not only do the krewes participate in the parades, but, as leaders of New Orleans society, they also hold balls and other elaborate events during the carnival season, which lasts from Christmas up to Mardi Gras itself. The krewes used to be responsible for electing Rex, the annual king of the carnival, whose parade is the climax of Mardi Gras. This practice is no longer observed. While masked paraders had long been a part of Mardi Gras, the first carnival group organized as such was the Mystick Krewe of Comus in 1857. Krewe is only a fanciful spelling of crew in its standard meaning, but the word, thanks to its association with Mardi Gras and New Orleans high society, has taken on some of the mystique of the carnival.

The word krewe has come lately, most incorrectly (mostly because of mis-information and mis-understanding ) to mean any Carnival group or organization.

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What a Krewe is not !

Technically, If the organization or group, fails to do, any  one  of the following;

(a) holds a parade which, (b) utilizes floats and/or bands (c) has the celebration of Carnival as it's main purpose. (d) holds a ball,

they are said not to be a Krewe. They are  rather said to be a Carnival organization, club or group. Examples of non-krewe clubs and org's are, Second Line clubs, the Mardi Gras Indians, Marching clubs, other various  other groups.

  There are no exceptions, to this rule. Yes! Comus, Momus, are now organizations, not a Krewe, as is the Original Illinois Club, and any group that does not parade, becomes an organization the day they stop parading. 

Also see " What is Mardi Gras ? "