What are those buttons?

There are three buttons above the power on button on my all in one. I have no idea what they are for. I've looked at them with a flashlight and magnifying glass and see nothing indicating what they are for. 

I expected to get some kind of material with my shipment from Dell that would provide such information. I'm not sure I have ever bought a computer that didn't come with such information. 

I have checked out user guides and can't find this particular information in them. 

I should be easier to get such information. It seems a bit extreme to have to find a support forum to ask questions about a matter like this. And I don't even know if I can get the answer here.