What is the action between the President and another head of state called? Does this action require congressional approval?

It would depend upon the "action". Heads of state often meet and discuss a course of action. It is called

"diplomacy". These meetings do not require congressional approval.

What is the action between the President and another head of state called?

The action between the President of the United States and another head of state is typically referred to as diplomatic engagement or a diplomatic encounter. This can take the form of meetings, negotiations, or discussions aimed at fostering relationships, addressing international issues, or advancing foreign policy goals.

Regarding the requirement for congressional approval, it depends on the specific action being undertaken. The U.S. Constitution grants the President considerable latitude in conducting foreign policy, but there are instances where congressional approval is necessary, particularly if it involves significant commitments or actions.

For example, if the President wants to negotiate and enter into a treaty with another country, the Constitution requires that the treaty be approved by a two-thirds majority in the Senate. This is stipulated in Article II, Section 2 of the Constitution. The Senate serves as a check on the President's power to form international agreements, ensuring that there is broad support for such commitments.

On the other hand, routine diplomatic engagements like meetings, summits, or discussions with other heads of state generally do not require specific congressional approval. The President has the authority to engage in such activities as part of his role as the chief diplomat of the United States.

It's important to note that the specific circumstances and actions involved can vary, and there may be instances where congressional approval is required on a case-by-case basis. Therefore, it is advisable to consult the relevant laws, constitutional provisions, or seek legal expertise to determine if a particular action requires congressional approval.