What is region monitoring?

I recently bought a new iPhone, iPad or iWatch and I'm wondering... What does region monitoring mean?

In iOS7 / iOS8 devices and newer, as well as newer Android devices, "region monitoring" is a method (using low power "Smart Bluetooth") to locate and pickup signals (values) from nearby iBeacons in stores / shops, shopping malls, restaurants, tourist attractions and other locations. iBeacons are commonly used to provide us consumers with specific information about nearby products and services, to be displayed on our smart phone or other smart device that has "region monitoring" enabled.

The region monitoring functionality, developed by Apple is also used if you would want to pay / checkout in a physical point of sale (POS) using your iPhone or Android smartphone (mobile payments).