The following is a brief description of the two chambers of Congress and what their functions are:

House of Representatives

The lower body of the Congress. House members are elected to represent a geographic Congressional district for two-year terms. The US House, with 435 voting members and five nonvoting delegates, is much larger than the Senate, with 100 voting members. The number of representatives each state has is dependent upon the state's population, and can change every 10 years based on the results of the US Census. The House is seen as the more personal branch, as House Members have smaller constituencies and are the direct link to the Congress of the United States. House Members consider bills based on how they will affect the constituents in their districts.

The House's most powerful function is presenting all spending bills or appropriations. This power starts in the House, but needs to be agreed upon in the Senate for these bills to pass.

Senate

The upper body of the Congress. Each state has two US Senators elected at-large, to serve six-year terms, with one-third of the seats up for re-election every two years. Senators are less inclined to vote on short term passions of a smaller constituency in their state, due to the fact that they are more insulated and hold the seat for six years.

The Senate's most powerful functions include providing advice and consent to the President on foreign policy matters such as war, and on political appointments such as judges.

Dividing Congress into two chambers was part of the Founders' intent to implement checks and balances in the government, requiring a positive vote of both sides to approve legislation. By designing differences into both the House and the Senate, the founders assured that legislation would be carefully considered in both the short and long term.

Source: Parent Project Muscular Dystrophy