A screenshot also known as screen capture or screen shot, is an image of the visual items displayed on a computer desktop, laptop, android, iPhone or windows mobile phones, television. There is built-in functionality that records or graphically capture the screen dump or screen-grab in Android, Windows, MAC, iPhone, Amazon Kindle chrome os and Blackberry.
Taking screenshots in:
Windows Phone : Power + Volume UP Button at the same time.
Xbox One : Double press the Xbox button.
Windows 7, 8, 8.1, Win-10, XP : Press PrtSCR button from the keyboard.
Android : Home + Power OR Volume Down + Power OR Back + Power button. You can Press the power button for some time a pop menu will appear having Screen-shot as one of the option (Android KtKat 4.4, Lolipop 5.1 or Marshmallow 6).
Chrome OS : Ctrl + f5 OR Ctrl + Shift + F5.
iOS : Press the Home + Lock button at same time.
Linux : PrtScr (print screen button from the keyboard)
OS X / 10 : Cmd + Shift + F3
Maemo 5 : Ctrl + Shift + P