The French and Indian War had cost the British a bundle. This war was fought in the American colonies. Assisted by Native Americans, the British won. They gained a lot of land in the colonies, formerly controlled by the French. But they had borrowed a considerable amount of money to fund the war. And, they had many British troops left over from the war still stationed in the colonies. Care of those troops was draining them financially.
The Proclamation of 1763: British Parliament passed a law called The Proclamation of 1763. The Proclamation was an attempt to establish a western border of the 13 colonies in America. That border was the Appalachian Mountains.
The Proclamation made it illegal for colonists to settle west of the Appalachians, illegal to move into Ohio or Tennessee or Florida. Parliament was hoping this would satisfy the Native Americans in the area, and reduce the need for troops along the border to protect colonists from Indian attacks, which would of course save the British money.
It sounded like a good plan, but the law did not succeed because so many settlers had already begun to move west. (A few years later, the law was changed to recognize western settlements.)