There are several options for taking a screenshot on a Chromebook with the Chrome OS.
1- The fastest option is to use the key combination Ctrl + 
Your Chromebook or Chromebox captures the entire screen and saves it as an image in your Downloads folder.
2- Another option is to use the keyboard combination Ctrl + F5, in this case a capture of the whole screen is also made and saved in the Downloads folder.
To take a partial screen capture there are also two options:
1- Hold the Ctrl + Shift keys and press and use the mouse to select the area you want to capture, it will be saved as an image in the downloads folder of your Chromebook.
2- Press and hold the keys Ctrl+ Shift and press F5 and use the mouse to select the area you want to capture, it will be saved as an image in the downloads folder of your Chromebook.
Once the screen capture is done, a notification will appear indicating that the screen has been captured and the option to open it.
If you want to take a screenshot on tablets with ChromeOS: press the power button + the volume down button.
