NORAD Santa Tracker is a public service offered by that organization. Each year, NORAD tracks the geographical location of Santa Claus as he makes his annual trip delivering gifts to children around the world, and makes that information available to the general public through a phone service and various channels online.
The North American Aerospace Defense Command (NORAD) is a bi-national United States and Canadian organization charged with the missions of aerospace warning and aerospace control for North America.
According to the official web site, the NORAD-U.S. Northern Command (USNORTHCOM) Command Center serves as a central collection and coordination facility for a worldwide system of sensors designed to provide the commander and the leadership of Canada and the U.S. with an accurate picture of the airspace above the U.S. and Canada. The commander is appointed by, and is responsible to, both the U.S. president and the Canadian prime minister.
Although most data collected by NORAD is top secret, each December 24th, volunteers at NORAD share the data they collect about one specific object in space -- a red sleigh led by eight tiny reindeer (nine if it's foggy). What started as a typographical error in a newspaper ad has become a tradition for many children across America and Canada. According to the special NORAD web site, NORAD uses four high-tech systems to track Santa – radar, satellites, Santa Cams and fighter jets.
Children can visit the special NORAD website with their parents and use a special version of Google Earth to track Santa.
Colonel Harry Shoup explains how the Santa Tracker got started in in this video from NORAD.