a marketing/advertising scam designed to get you shopping for christmas sooner then you normaly would, in the hopes that if you are out shopping 30 days before christmas it will spread out the demand on the supply chain for the stores. instead of the normal 2 weeks prior to christmas where everyone does their shopping and shelves are empty near christmas day. they want you to start shopping in november so that their books look better for that month, historically there really isn't much shopping done in november because everyone is saving their money to buy christmas presents in december. all in all its to get you to spend your money.
september 24th 1869 was the first day coined as black friday. due to a collapse of the gold market because of scandal that went all the way to the president of the u.s. http://en.wikipedia.org/wiki/Black_Friday_%281869%29