The Virginia Plan proposed that larger populated states deserved larger representation. They also believed there are 2 houses in legistature. This plan was supported by larger populated states, but not by smaller states.
The New Jersey Plan proposed equal representaion no matter the population in a state. This idea was supported by smaller states but opposed by larger states who agreed with the Virgina Plan. The New Jersey Plan also proposed only 1 house in legistature.
The Great Compromise between the Virgina Plan and the New Jersey Plan proposed that there would be two houses of legislature and that there would equal representation in Congress (Senate). Additionally, Representaion in the lower house was based on population.
The Northern States and Southern States faught about slaves counting as a part of the overall population and so the 3/5 Compromise was: out of the five slaves, only three of them count as a part of the population. As free men.