On Windows by default you can press PrintScreen (PrtScn) on the keyboard to copy the current screen to the clipboard. This can then be pasted into any document or as a file. You can also do WindowsKey + PrintScreen, to save the current screen to a file location of your choosing instead.
You can also use the "Snipping Tool" which can be found in the Start Menu by searching for it. This will allow you to select the area of the screen you would like to screenshot instead.