The Great Compromise of 1787 was an agreement reached between delegates of the states with both large and small populations. Under the plan, the Legislative Branch would consist of a bicameral body (two chamber), with each state getting a number of representatives in the lower chamber, based on the state's population (the House), and two representative for each state in the upper chamber (the Senate). This is the way in which our Congress continues to be ran to this date.
The Compromise was a blending of both the Virginia Plan and the New Jersey plan. The Virginia Plan was supported by larger, more populous states, who wanted Congressional members to be elected based on each state's population The New Jersey plan, which was supported by smaller, less populous states, desired that each state have equal representatives serve in Congress, regardless of population.