Congress is divided into two chambers, the Senate and the House of Representatives. The Senate is sometimes called the upper chamber and the House the lower chamber because the Founders thought that different sorts of people would be elected to these two bodies. House members face elections every two years in smaller districts, so the Founders thought that representatives would be closer to the people. In contrast, Senators were originally chosen by state legislatures, and with elections every six years and steeper eligibility requirements, the Founders believed that the Senate would serve as a voice for the nation's wealthy and established interests.
To a certain extent, the Founders correctly predicted differences between the two chambers. The Senate is more deliberative, with strict rules to encourage debate, and it follows decorous norms of behavior like those of some exclusive club. The House is a bit rowdier, allowing confrontational leaders like former House Speaker Newt Gingrich to rise in influence.
But in other ways the Founders were mistaken. Senators have been directly elected by voters since the Seventeenth Amendment passed in 1913 and are much more likely to lose reelection campaigns — so they must work harder to curry favor if they want to keep their positions. Members of the House, by contrast, seldom lose their reelection bids unless they have been marked by scandal or their districts have changed. They are more insulated from the popular passions that America's Founders feared they would express.