What Does this button do?

As a well-educated person, I CAN assure you that I already have checked with my salesperson. He evidently went on vacation before he could follow through with me, and so I really thought that a large community such as this MIGHT be able to answer my inquiry a bit sooner in a nice way without dissing or lecturing me. I signed on here to gain knowledge, some of which I also may be able to share should I someday have an answer to another's question. This unknown and unnamed button (yes, I ALSO looked through the 700+ page manual (PDF) without success! So if anyone knows the answer I will be very grateful and thankful. Is there ANYONE in this community that knows what this button does??!!

We have a winner! Someone who read the manual!

Sorry guys, I meant smth different.

there is a round button in the cargo section of the car on the driver's side. The button has a 'sound' icon on it. Push it in, and the car will beep as you approch something to the rear of the car. Push it out and the beeping sound will be turned off. The grid lines on the navigation screen still appear whether the sound is on or off.