From Wikipedia:

The Speaker is second in the United States presidential line of succession, after the Vice President and before the President pro tempore of the U.S. Senate.[3] Unlike in some Westminster System parliaments, the Speaker is a leadership position in the majority party and actively works to set that party's legislative agenda, therefore endowing the office with considerable power. The Speaker does not usually personally preside over debates, instead delegating the duty to other members of Congress of the same political party.[4] Aside from duties relating to heading the House and the majority political party, the Speaker also performs administrative and procedural functions, and represents his or her congressional district.