Modern smartphones rely on the Global Navigation Satellite System (GNSS) for accurate positioning and location services.
The GNSS is a generic name for any of the available global systems of satellites providing signals from space where positioning and timing data is transmitted to the devices so they can determine their own location.
The most popular examples of GNSS include Europe’s Galileo, the USA’s NAVSTAR Global Positioning System (GPS), Russia’s Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) and China’s BeiDou Navigation Satellite System.
Each of these systems has global coverage so if a smartphone supports all of them, it has a higher chance of having readily available satellites to connect to.
Devices, which are not equipped with built-in GNSS receivers, can still get approximate location information by using Wi-Fi & cellular radio by scanning the available access points/cell towers in the vicinity. However, unlike GNSS, this location information is not accurate enough to be used for navigation.