The Stamp Act was a law introduced in the colonies by the British Government on March 22, 1765. It required all colonists to pay a tax on every piece of printed paper they used, from newspapers and playing cards to maps and legal documents. The purpose of this law was to raise £60,000 every year, which the British could put towards the cost of maintaining their troops who were stationed at various posts across the American colonies. The British also used the Stamp Act as an opportunity to create local jobs, by appointing Americans to collect this money--a move that they hoped would appease the colonists.
In reality, however, the Stamp Act greatly angered the colonists because it seemed to them like a huge injustice. At its heart it was unconstitutional: every English subject had the right to be taxed by his chosen representative, not taxed under a law that he had not voted in favor of.
Ultimately, the Stamp Act was the first piece of legislation which had a dramatically negative effect on Britain and her colonies. Over the next few years, the Sugar Act of 1774, a tax on molasses, and the Declaratory Act of 1776 only served to exacerbate these tensions and set the stage for American independence.