As wantmygti stated. It's properly called "Interior Monitor and Anti-Tow" protection.
Switch off ignition and remove key > open drivers door > press the button to illuminate the LED in the button > close all doors, and lock. The interior ultrasonic sensors are turned off, so you can leave dogs, small children, the granny, in the car. The Anti-Tow, using the tilt-sensor is also switched off.
The next time you unlock and lock, the alarm defaults back to the full protection. You have to press the little button each time you need to turn off those particular functions.
HTH, rgds