The Speaker of the United States House of Representatives is the presiding officer and parliamentary leader of the lower house of the U.S. Congress (currently Nancy Pelosi). The house Speaker is elected by the party that has a majority in the House of Representatives. The Constitution does not require the speaker to be an incumbent member of the House of Representatives, although every speaker thus far has been.
In the event of need, the U.S. House Speaker is second in line (after the Vice President) to act as President.