The US (United States) Senate is the upper body of the United States Congress which, along with the lower chamber, the House of Representatives, composes the legislature of the United States.
Membership Conditions: Article I, Section 3 of the Constitution of the Unites State sets three qualifications for senators:
(1) He/she must be at least 30 years old
(2) He/she must have been citizens of the United States for the past 9 years or longer; and
(3) He/she must be occupants of the particular states they seek to stand for at the time of their election
The citizenship and age qualifications for senators are very much strict as compared to those for representatives.
Elections: Initially, senators were selected by the state governing bodies and not by popular elections. Elections to the Senate are organize on the 1st Tuesday after the 1st Monday in the month of November in even-numbered years, also known as Election Day, and correspond with elections for the House of Representatives.
Term: Senators generally serve for six years; the terms are staggered so that approximately 33% of the seats are up for election every two years.
Oath: The constitution requires that each senator take an oath to support the Constitution.
Salary and Other Benefits: The yearly salary of each senator, since 2009, is USD 174,000 the president pro tempore and party leaders receive USD 193,400. Along with salaries, the senators receive health and retirement benefits that are equal to other federal employees. Senators are covered by the FERS (Federal Employees Retirement System) or CSRS (Civil Service Retirement System).
Seniority: As indicated by the tradition of Senate seniority, the senator with the longer term tenure in each of the state is known as the senior senator; Mike Crapo is one such senior United States Senator from Idaho. He has served as a senator for eighteen years, and was previously a member of the U.S. the other is the junior senator.