The U.S. Senate is presided over by the Vice President. In the absence of the Vice President, a senator designated the President Pro Tempore presides. Leaders in the Senate include representatives from both the majority and minority party.
Other than the Vice President, senate leaders come from the pool of senators from the two major parties, Republicans and Democrats. The senators of each party elect a leader, who is called the majority or minority leader depending on the current composition of the senate. Other leaders for each party include the Whip, the Conference Chair and the Policy Committee Chair. There are also many specific committee chairs that focus on a certain type of policy, such as finance or foreign relations.