Current Screen (only visible on a multi-screen environment)
Everything on the single screen is captured, usually used for desktop screenshots.
Full Screen
This works differently, depending on whether you have a single screen or a multi-screen environment. For single screen users it captures everything currently on the screen. Multi-screen users will see it capture all screens into a single window.
Window Under Cursor
The content of an applications or dialog window is captured. usually used for application screenshots. Preferably, check the Include window decorations option (2).
Region
Only a region to be defined later is captured.
Click on New Snapshot (3).
Full Screen
Current Screen
Window Under Cursor
Click anywhere on the screen to take the snapshot.
Region
Use the mouse to draw a rectangle around the region to be captured (for example around a window).
Strike the Enter key or double click in the region to take the snapshot.
Click on Save As... (4).
Browse to the location you want to save the image, give it a name (name.png) and click on Save