Each of the 50 states sends 2 people to the Senate, so there are a total of 100 senators. This means that each state has equal representation in the Senate. Each senator serves a term of 6 years. When their 6 year term is over, the people from that state may choose to elect a new senator or keep the same one. There is no limit on the number of terms a senator can serve.
The Senate has special jobs that only it can do. It can: