What are the three buttons above touchpad in the Dell Latitude E6520 laptop?

I wonder what are the three buttons added to the touchpad/keyboard of the laptop Dell Latitude E6520 as the below snapshot.

I do a google search as here though nothing helpful for me.

If you know that they are, please share.

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The buttons on the left and right are left and right clicks for when you're using the "pointing stick" between G, H, and B.

The middle button will either be a middle click, some sort of scroll, or a "lock" for the left click to make clicking and dragging easier.


They are the buttons that go with the trackstick.


Source Setup and Features Information:

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