Why did James Madison propose the Three-Fifths Compromise? What was the compromise?

Three-fifths compromise, compromise agreement between delegates from the Northern and the Southern states at the United States Constitutional Convention (1787) that three-fifths of the slave population would be counted for determining direct taxation and representation in the House of Representatives.

James Madison was trying to compromise if a slave should represent a person, or not, while conducting a census to determine how many electoral votes each states gets. It basically stated that every person of color, was worth only 3/5 a man, rather than a whole.