The President of the United States issued a proclamation to honor Pope Francis, ordering that the American flag be flown at half-staff. This order applies to the White House, all public buildings and grounds, military posts, naval stations, and vessels in the U.S. and its territories. Furthermore, the flag shall also be flown at half-staff at U.S. embassies, consular offices, and military facilities abroad until sunset on the day of Pope Francis's interment.
Simple Explanation
The President has asked that people in the U.S. and around the world lower their flags to half-way up to honor Pope Francis after he passed away, and this will continue until he is buried.