The Bill of Rights is the name of the 1791 document containing the first ten amendments to the U.S. Constitution.
Congress proposed twelve amendments on September 25, 1789, largely in response to Anti-Federalist concerns that the new Constitution did not adequately protect individual liberties. The states ratified ten of those articles on December 15, 1791, creating Amendments One through Ten.
The amendments protect freedoms and establish safeguards involving religion, speech, press, assembly, firearms, searches, criminal prosecutions, trials, punishment, and reserved powers. James Madison played the leading role in drafting and guiding the proposals through Congress.
A common mix-up is that Congress originally proposed twelve articles, not ten. The first and second proposed articles were not initially ratified; the original second article eventually became the Twenty-seventh Amendment in 1992.