The Vice President of the United States is the designated President of the Senate as is set forth in the US Constitution. However when the Vice President is away then the Senate's president pro tempore (or any others so designated) is the acting President of the Senate. For any vote in the Senate that ends in a tie, only the Vice President can cast the tie-breaking vote.
The vice president of the US is president of the Senate even though he is not a member.
The office is Senate pro tempore. He is elected by the Senate. The current custom is to elect the majority party member with the greatest seniority in the Senate.
Legislative
The Vice President is also the President of the Senate, but he can only vote if the other senators are tied.
The Senate can remove Federal officials from office. The Senate is responsible for initiating an impeachment of a President of the United States. The Senate can also vote to have a member of the Senate removed for misconduct.
The president pro tempore of the Senate is elected by the Senate, and by tradition the majority party elects their party member who has the longest seniority in the Senate. He is a voting member of the Senate unlike the VP. Most of the time who presides over the Senate is irrelevant.
Cabinet members are appointed by the President; with Senate approval.
The senior member of the majority party of the Senate, who would then be the President Pro Tem of the Senate (or President pro tempore for the full name)
The Vice President of the US is the Senate President, however, he can appoint or delegate any of the senators to officiate on his absence which is called the President's Pro Tempore. The 113th Congress Presidents Pro Tempore as Jan 3, 2013 is Patrick J. Leahy.
In the US, you become President of the Senate by becoming vice-President of the United States.
The U.S. Constitution requires that the Senate have two officers. Theses are the President of the Senate, which is the Vice President of the United States, and the President pro tempore, which is traditionally the senior member of the majority party in the Senate.
the president of the senate is not a member of the majority party