A lot of people want Windows 10 to take a screen shot like their phone does. They want the machine to pop up the screen shot or a message saying "Yep, we got us a screen shot." when in fact the buttons DO work properly.
ALT+ Print Scrn takes a screen shot of the current active window, this includes error messages.
CTL+Print Scrn takes a screen shot of the entire window (or two, if you have double monitors.)
Now, in order to SEE or UTILIZE the screen shot, you must use another program. MS Word, or better yet, MS Paint. (MS Paint is available in Windows 10) Just open the program and press CTL+V (Paste) and you will see your screen shot.
Better Yet: Use Snipping Tool/Snip and Sketch Tool
Use the search bar next to the Start Button and type SNIP.
Select Snipping Tool or Snip and Sketch from the list.
When the program opens you can now use it to take a screen shot of all or part of the screen. You can even add arrows, or highlight using Highlighters tools. It's easy then to save your file and/or attach it to an email.