Answer: Whether the states' representation should be equal or proportional.
Explanation/detail:
The Great Compromise was a measure decided during the United States Constitutional Convention in 1787. The Great Compromise resolved a dispute between small population states and large population states. The large population states wanted representation in Congress to be based on a state's population size. (This was the essence of the Virginia Plan.) The smaller states feared this would lead to unchecked dominance by the big states; they wanted all states to receive the same amount of representation. (This was the New Jersey Plan.)
The Great Compromise created a bicameral (two-chamber) legislature, with different rules for representation in each chamber. Representation in the House of Representatives would be based on population. In the Senate, all states would have the same amount of representation, by two Senators.
