There were two plans suggested for the representation in Congress.
One was the Virginia Plan, and the other was the New Jersey plan. The Virginia plan suggested that the states should get representation based on their population, and the New Jersey plan suggested the states would get equal representation.
Smaller states of course would favor the New Jersey plan, because they didn't want to lose power in Congress.
They ended up compromising on this. They made the House of Representatives, which used the Virginia plan, and the Senate, which used the New Jersey plan. (The Senate has more power than the House of Reps)