The Great Compromise solved issues between states with small populations and states with large populations.
The Great Compromise was developed at the Constitutional Convention and helped in creating the modern day structure of Congress. In this deal, both states with small populations and large populations got something they wanted. For example, the Senate would be composed of 2 Senators from each state, regardless of their states population. This helped to ensure that smaller states had a voice in the creation of federal laws.
On the other hand, the House of Representatives would have the number of representatives based on a states population. The greater the population, the more representatives. This made larger states happy, as they felt this accurately represented the power they should have in Congress.