Most standing committees have subcommittees. Most of the work gets done in subcommittees. Each subcommittee specializes in a subcatagory of its standing committee. For example, the Senate Foreign Relations Committee has a subcommittee that deals with European Affairs, another deals with the Western Hemispere and Peace Corps Affairs, etc. Simply put, subcommittees specialize in a particular policy area and report back to the main (standing) committee. Many members of Congress want to become chairpersons of subcommittees because they can get so much done, accomplish something important to them, gain prestige, and even improve their image with the voters back home.