Android devices can determine your location in the world (for example, your current address) using a number of different methods. These settings control which methods should be used, and how apps can use this information.
See Location settings for Android 4.3 and earlier for location settings on older devices.
On / Off
The main on/off switch inside the location settings provides a way to completely disable location services.
When disabled, no app on your device, including Google apps like Maps, will be able to know your location either by GPS, Wi-fi or mobile networks.