The Government of Great Britain, Parliament, needed money to pay off the cost of the Seven Years War, known in the colonies as the French and Indian War. They believed that the colonists should help pay this cost since much of the fighting was done to defend them.
So Parliament passed the Sugar Act, which was a tax on sugar, wine, indigo (a type of color dye) and molasses. The last was very important to New England merchants, since they bought molasses to make rum to sell to other colonies including the French, Dutch, and Spanish. This tax almost stopped the rum trade from New England, and the New England colonies protested. The rest of the colonies didn't see what the big fuss was all about.
But the tax worried colonial leaders. They feared Britain might be moving towards seizing power from colonial governments, such as the right to tax. The colonial leaders did not want that to happen. They wanted the American colonies free to govern themselves as they had been doing for many years.