The purpose of a bicameral legislature is to represent two differing interests, according to the Encyclopedia Britannica. Wikipedia states that a bicameral legislature also provides checks and balances, and it prevents the passage of bad legislation.
Wikipedia notes that the concept of a bicameral legislature started in Medieval Europe and was meant to represent groups of different social orders. The Encyclopedia Britannica notes that the bicameral legislature that started in Britain represented the interests of the nobility and common man in two different houses, and the same system was started in the United States.
Wikipedia adds that a bicameral legislature typically calls for a concurrent majority for legislation to pass. A concurrent majority allows minority members to block or veto legislation, and it is meant to stop the majority from oppressing the minority. The founding fathers of the United States established separation of powers in the Constitution, including a bicameral Congress. The purpose of a bicameral Congress in the United States was to strike down popular movements that infringed on the rights of those in the minority.
Wikipedia reports that Senate members were chosen by state legislatures, and House members were elected by the populace. The framers of the Constitution argued that a Senate was needed because wiser men among the ruling class were necessary for reigning in the passions of the House. However, the 17th Amendment to the Constitution stated that senators must be elected by the population as well. Discussions from the Great Compromise rebranded the Senate side of the bicameral legislature as equally representing the states.