Unlike Windows, Ubuntu has a snipping tool of it’s own.
It’s named as gnome-screenshot.
Have a look at Screenshot. You can find it in Ubuntu Software.
http://apt.ubuntu.com/p/gnome-screenshot
However, there’s also a shortcut key associated in Ubuntu for taking snippets.
Hold down the Shift + PrtScn keys together.
Your mouse will change to a cross-like pointer.
Hold down your left-click key on the mouse and drag.
This uses gnome-screenshot behind the scenes.
You can change the keyboard shortcut via the regular keyboard settings.