GPS (Global Positioning System) is a satellite navigation system owned by the United States government that currently includes 24 operational satellites. GPS works in all weather conditions, anywhere in the world, 24 hours a day and has no subscription fees or setup costs.
GPS satellites rotate around the Earth in about 12 hours in a precise orbit. Each satellite transmits a signal including unique orbital parameters that allow GPS devices to decode them and calculate the satellite's precise position in space. GPS receivers use this information and the trilateration method to calculate a user's exact location on the Earth's surface.
Modern GPS receivers are extremely accurate, thanks to the use of multiple channels working in parallel. We can say that the accuracy of GPS receivers is approximately more or less 5 meters.
There are other GPS-like systems around the world, all classified as Global Navigation Satellite Systems (GNSS). GNSS is a generic term that refers to all satellite navigation systems. Most receivers can use GPS, GLONASS and Galileo, and some models even BeiDou and QZSS.