To be able to effectively answer this question you must first understand what the first two plans were.
The Virginia Plan was a plan that would favor larger states in the legislative branch. It effectively based representation in those branches solely off of population, which would severely hinder smaller states representation in Congress. This system would also be a unicameral house; a single house system.
The New Jersey Plan was a plan that would even out the differences between the smaller states and larger states by providing that everybody have an equal amount of representatives in Congress. Therefore, each state, regardless of population, would have a certain amount of lawmakers from their state. This system was also a unicameral house; a single house system.
These two plans share a clear resemblance to the current system we have today. This system, also called the Connecticut Compromise by those at the Convention, was a compromise that incorporated the major aspects of both plans. It employed a bicameral house; a house system with two separate houses. One house, the Senate, would be based off the New Jersey plan and have equal representation for all. The other house, the House of Representatives, would be based off the Virginia Plan and provide the number of representatives for each state based off of population.
Fun fact: Every 10 years the federal government determines how many seats a state gets in the House through the US census.
Heated debate led to an overwhelming pro-secession vote. Georgia's declaration of causes made it clear: the defense of slavery was the primary cause for dissolving the Union. Future Confederate Vice President Alexander Stephens warned the decision would lead to war.
