Duties of the House and Senate are apportioned by the US Constitution.
Enumerated powers are specified under Article I, Section 8. Implied powers are contained under the Necessary and Proper Clause. The House and the Senate share the power to declare war, raise an army and navy, borrow and coin money, regulate interstate commerce, create federal courts, establish rules for the naturalization of immigrants, and "make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers."
The Constitution creates a checked and balanced relationship between the House and Senate.
The House alone has the power to originate revenue bills. However, this power is restrained because the House and the Senate must approve all (including revenue) bills. The House of Representatives has the power of impeachment, which is the power to formally charge the president, vice president and other national government civil officers with serious crimes. The Senate is empowered as the court to try impeachments, with the chief justice of the Supreme Court presiding. A two-thirds majority Senate vote is required for impeachment.
The Constitution creates a checked and balanced relationship between the Senate and President.
The Constitution gives the Senate power to approve major presidential appointments such as federal judgeships, ambassadorships and cabinet posts. Also, the Senate has power to approve treaties with foreign nations. While the president may make treaties, they require approval (two-thirds majority) from the Senate. Thus, the executive branch accounts for the Senate's ideology when negotiating a treaty.