GPS (Global Positioning System) and GLONASS (Global Navigation Satellite System) are two systems of satellites with the primary objective to provide an accurate positioning in terms of latitude, longitude and altitude to any reciever on the planet surface.
GPS is a system launched and maintained by the US while GLONASS by Russia. GPS was launched four years earlier than GLONASS. The latter began production in the USSR days back in 1976 and was launched in 1982. GLONASS after being refueled in Vladimir Putin’s precidency has put up all 24 geostationary satellites required to provide complete coverage. GPS on the other hand was launched with 22 and now has 31. GPS is overall considered to have a better accuracy though GLONASS has a better accuracy as we go closer to the poles.