Remember the old days when you could tap the "Print Screen" button on your keyboard and your printer would just take off printing whatever you were looking at?  Of course Windows changed all that because while DOS is text, Windows is graphics .. or pictures.  So now when you tap the Print Screen button nothing happens.  Or it SEEMS like nothing happens.  But if you then open the little Paint program that comes with all Windows versions, you can then click the Edit Menu and then "Paste" .. and voila!  What ever you saw appears in front of you .. it's called a Screen Shot.  I use it to make little pictures of error messages I get.  Only then, I tap "ALT" and the "Print Screen".  That captures only the active window .. and not the whole desktop as I did below.