The software will look-up Cell-tower cell-ids and indoor Wi-Fi and Bluetooth MAC addresses in the local database, perform trilateration based on signal strength, and then return a geographical coordinate (latitude, longitude) which is the most likely position of the device as a response to the API request. The error of the location depends on the density of radio transmitters. A typical median error for outdoor Cell-ID positioning is around 150m in urban areas, which is world class compared to any other geolocation service.

The Combain global database includes millions of cell-ids from all around the world. You select how much of this data to be licensed and used in your local instance of the database.  

195 countries 

> 140 million cell-ids (GSM, WCDMA, LTE, CDMA) 

> 111 billion positions