Print Screen or Screenshot the Active Application Window

To print screen the active application window you can press ALT + PrtSc on your keyboard.

Please open the window that you want to print screen.

Click ALT + PrtSc on your keyboard. Paste on your document for example Microsoft Office Word or Paint. The result like that.

It can be concluded:
PrtSc to print screen all the displays on the screen.
ALT + PrtSc to print screen the active application window.