The excerpt you provided is an example of the separation of powers principle enshrined in the U.S. Constitution. This principle delineates the distinct roles and responsibilities of the three branches of government: the executive (headed by the president), the legislative (Congress, which includes the Senate), and the judicial.
In this context, the president has the power to make treaties, but this power is not unilateral. It requires the advice and consent of the Senate, specifically a two-thirds majority of senators. This illustrates how the legislative branch and the executive branch must work together to make significant decisions, thereby preventing any one branch from having unchecked power and fostering a system of checks and balances.