The original Bill of Rights ratified in 1791 contained ten amendments to the United States Constitution.
James Madison introduced a larger package of proposed amendments in the First Congress in 1789. Congress approved 12 proposals and sent them to the states, but only 10 were ratified by the required number of states at that time. Those 10 amendments became known collectively as the Bill of Rights.
The amendments protect freedoms and set limits on government power. They address religion, speech, press, assembly, arms, criminal procedure, civil juries, and other rights. The Ninth and Tenth Amendments also address rights retained by the people and powers reserved to the states or the people.
The two proposals that were not initially ratified had a different fate. One concerned congressional apportionment and remains unratified, while the other eventually became the Twenty-Seventh Amendment in 1992. That later development is why the Constitution now has 27 amendments, but the original Bill of Rights still has 10.