[ Thanks to PmaBox for this link.
]
“In reality, the print screen functionality in Ubuntu
comes with the main distro installation package and gets installed
by default. So, to Print a Screen any Ubuntu user just needs to
press PrtSc key of the keyboard, usually located on the top right
corner. On Laptop keyboards, to have the same effect, users usually
have to press fn key + PrtSc key, the fn key is located on the
bottom left corner and the PrtSc key is located in the top right
corner.“This is how a screenshot looks like:”