The Three-Fifths Compromise addressed a dispute over representation between slave states and non-slave states.
The Three-Fifths Compromise was a way of accounting (somewhat) for the population of slaves in states that permitted slavery. For taxation and representation purposes, the question was whether slaves should count in the population figures. (They were not considered voting citizens at that time.) The Three-Fifths Compromise said that three out of every five slaves could be counted when determining a state's population size for determining how many seats that state would receive in the House of Representatives.