Use the Move Selected Pixels tool after you have selected an area in order to manipulate its size and rotation or cut it out completely.

This can be used in conjunction with any of the selection tools. The Move Selected Pixels tool is very handy if you wish to isolate an area within a picture and move or rotate it:

The section of the photograph in the previous screenshot is selected using Rectangle Select and then moved using the Move Selected Pixels tool. This tool will move the pixels to another area revealing the layer underneath the current layer.

The Move Selection tool is handy if you want to move the selection to another part of the image.

Move Selection will not change the image. The following is a screenshot of a selection before and after the Move Selection tool has been used: