How does the Print Screen key work?

I want to know how the Print Screen key works. This is useful to take a snap of the current screen, but how does is this possible? Is there software that run and take a snap when print screen key is been pressed? If so what are they?

Can anyone help me in the behind scenes of this process?

Specifically how it works is implementation-dependent, but in many cases the framebuffer holds whatever is currently being displayed on the screen, so the simplest way to make a screenshot is just to take that chunk of memory and write it to a file. You can often do this (on Linux) with the command cat /dev/fb0 > 'filename' (where 'filename' is the image file you want to write).

The Journeyman is quite right. It is basically just a functionality of Windows. As soon as you press Print Screen, Windows will grab the color of all of the pixels on your screen (the little dots), and save it to your clipboard (where everything you "copy" (ctrl + c) goes), so you can paste it in Paint, or whatever program.

There's no special software or anything running, it's just Windows.