How to copy and paste within an image

When I first began to use photoshop 7.0 I could select an area and right click and copy.  I could  paste, flip, invert etc.    I find this so difficult now.  Out of all the things in photoshop I have learned I feel incredibly stupid asking this.  What is the easiest way to do this.  I am trying to use the rectangular marquee tool to select an area, copy and paste.  I right click the selection but can only cut it out or work with a new layer.

Sorry for such a stupid question.