The United States Senate is part of the United States Congress , which is a group of people elected to decide the laws of the country. Every state in the US elects two people to represent them in the US Senate. These people are called senators. Since there are 50 US states, there are 100 senators.
Senators serve six years at a time, and one-third of them are picked every two years. The Vice President of the United States is in charge of the Senate, but only does anything when there is a tie vote or a special event.
In order to be a senator, a person has to be 30 years old or older, and has to be a citizen of the United States for 9 years or more. He or she must also live in the state they represent at election time.