Once a selection has been made, it can be moved and transformed in a variety of ways.
If you have a selection in place, you can move and transform it, and the pixels it encompasses, using the Move Tool. Furthermore, with the Move Tool active, the Transform panel can also be used for precision working.
If you're looking to reposition a selection, but leave the pixel content untouched, you can use the Marquee tools. However, if you wish to transform your selection while leaving the pixel content untouched, you need to enter Quick Mask mode. Once in Quick Mask mode, you can resize, reposition, rotate or shear a selection using the Move Tool or Transform panel.