The Bill of Rights is the first ten amendments to the U.S. Constitution. This collection of amendments certifies basic fundamental rights for all citizens. These include freedom to practice religion, freedom of speech and of the press, and protection from unreasonable searches.
The original Constitution did not have these basic rights codified within the document itself. A number of delegations and states felt this was an oversight. At the time, political leaders largely fell into two factions of Federalists and Anti-Federalists. Federalists supported a central constitution to govern all the states and were opposed to a bill of rights. The dissenting minority of Anti-Federalists opposed a constitution that provided too much federal power without encoding specific protections for all citizens.
In the end, the existing Bill of Rights came about as a compromise that allowed the nation to avoid yet another Constitutional Convention. Originally, 12 amendments were offered, but only 10 were ratified at the time. The first of the two articles was never ratified and dealt with proportions of Congressional representation per population. The second, regarding Congressional pay, was ratified over two centuries later in 1992.