GPS uses 24 satellites operated by the US Department of Defense to provide location services globally. GPS satellites transmit radio signals that include time and position data. GPS receivers triangulate their position by calculating the time delay of signals from multiple satellites. Factors like atmospheric conditions, signal multipath, and receiver clocks can cause errors, but differential GPS can achieve accuracy within 5 meters. GPS has many applications including navigation, tracking, and data collection across industries like agriculture, aviation, marine, and more.