My parents gave me my car without really explaining much about all of the bells and whistles, so I've had to figure out what most things do by myself. What does the depressable A/C button on the far right that displays a circle formed by three arrows do?

I presume it's some sort of recycle air/internal intake button that, when depressed, takes in air from inside the car to cool rather than from the outside. I'm guessing the manual explains what it does, but I doubt the manual says what actually works better. In your experiences, does the air get cooler faster and stay cooler when the button is depressed or when it is not activated?