What was the compromise called that eventually led to the creation of the new government in 1787 during the Constitutional Convention?

What was the compromise called that eventually led to the creation of the new government in 1787 during the Constitutional Convention? Why was a Constitution needed and more importantly what tone or precedent would it create once such compromise was reached and confirmed as it relates to America then and now. Please include in your answers all of the issues, topics, and eventual resolution that formed the new government in America.