The constituents of each state directly elect two people who serve in the United States Senate for 6 years and, while serving, the members enact laws that reflect the interests of their state. Elections for the Senate are held every 2 years, but they are staggered so that the Senate composition gradually changes.
U.S. Senators have the power to introduce bills that can benefit that people that they represent, and they have the ability to vote against legislation that would be detrimental to the interests of their state. If the constituents feel that their Senators have done a poor job of representing them, they can elect new members when their 6-year term is complete.