The adoption of the Bill of Rights came about when individuals at the Constitutional Convention raised protest about the power of the federal government and the rights of individuals. These thinkers, called Anti- Federalists, were animated by the sense of individual freedom and believed that there should be as little intrusion as possible. In the wake of Shays' Rebellion, they believed that the new Constitution gave too much power to the federal government at the cost of individuals and local governments. On the opposite side of this debate were the Federalists. They were individuals who felt that the central government had to have power in order to operate effectively. Both sides stood in opposition to the other. The adoption of the first ten amendments to the Constitution, the Bill of Rights, allowed the Anti- Federalists to be able to live with the Constitution as it sought to solidify federal governmental power, but not at the hands of the individual's sense of entitlements in regards to their freedom.
They were trying to prevent the government from trampling on the people's rights. This was something that the people who wrote the Constitution were not too worried about, but their opponents were really worried about it and so the Bill of Rights was added as a way to protect people's rights.
The Anti-Federalists, especially, were worried about the power of a strong central government like that in the Constitution. They worried that it would be like the British government had been before the Revolution. So they insisted on having these rights spelled out in writing.
Bill of rights in the USA refers to the first ten amendments to the American constitution. These bill of rights became law on December 15, 1791.
The need for the amendment to the constitution arose from the fact that the original constitution of 1787, finally ratified by all the states on June 21, 1788, did not sufficiently provided for protection of individual rights such as freedom of speech, religion and press. The objectives of the Bill of Rights as laid down in the preamble of the Bill was:
to prevent misconstruction or abuse of its (government's) powers, ... And as extending the ground of public confidence in the Government ...
A complete text of the Bill of rights is available on the website referred below.