I will try to be brief : There is this app, a game (World of Warriors) that DO NOT ASK FOR PERMISSION TO TRACK LOCALISATION. In this same app, there is this offer, Tapjoy (in the app, not through the Tapjoy app), that asks you to check an ad, download an app, complete a survey etc, in exchange of some of the game currency. However, the offers change in function of where you are. French dont have the same as Italians that dont have the same as Americans etc ... I tried to change my language, my localisation, the degree of localisation (only GPS, only network, both), using a fake gps provider, a VPN (Tunnelbear, Hola and a tons of others), but it doesnt change anything at all. Do you have any idea of how this is working ? Again, the app does not ask for gps localisation !
This is a simple IP location lookup.
There are some services that offer so called IP2Country lookup that gives you the country of an IP address. For instance http://www.iplocation.net/ combines multiple services and presents you all results of their respective databases.
All of them will at least share the same country (probably the one you are currently in) and mostly your rough region.