The legislative branch of the United States government is composed of the House of Representatives and Senate. There are 100 members of the Senate, two from each state, that are elected by popular vote. Each senator is elected to a six-year term with these terms staggered so that approximately one-third of the Senate is up for re-election every two years. There are 435 voting members of the House.
The House of Representatives also has six non-voting members that represent Puerto Rico, the District of Colombia and four other American territories. The 435 voting member seats are distributed across the 50 states by population density. Members are elected every two years. The leader of the House is called the Speaker of the House and is elected by the members. The Speaker is third in line to the presidency. The leader of the Senate is the Vice-President of the United States.
Each part of the legislative branch has different responsibilities. The House can elect the president in the event of a tie, introduce revenue-generating bills and impeach federal officials. The Senate can ratify treaties, except trade treaties which also must be approved by the House. It can also try federal impeachment cases referred by the House and confirm appointments to office suggested by the president. Combined as the Congress, the legislative branch of government has to approve bills in order for them to become law.