Gnome

How do I take a screenshot?

press PrtScn = GNOME captures the entire screen and asks you where to save it as a file.

Where can I find that key?

PrtScn ScrLk Pause Look for this group of keys at the upper right of your keyboard. Note: Print Screen (PrtScn) might have been abbreviated differently on your keyboard.

How do I make a screenshot of a single window?

hold down Alt and press PrtScn = GNOME captures the currently active window and asks you where to save it as a file.

I need more flexibility. How can I take screenshots using the command line?

try this: gnome-screenshot --help