You can work with a selected region in just the same way as you would with the whole image: draw within the selection, fill it with colors, apply transformations, effects and plug-ins as well as use gamma correction tools, adjust saturation, brightness and contrast.
You can also copy, cut and clear (Ctrl+D) selections using the controls on the main menu, main toolbar or hotkey shortcuts.
However, there's one difference between the whole image and its part. A selected part of the image may be moved within it.
There's a special tool on the toolbar window for moving selected regions. To move a selected area, choose the tool, click on the area and, holding down your left mouse button, drag the area to its destination.