Sometimes it’s helpful to save a picture of your Mac’s screen, or a portion of the screen, for a project, as a receipt or for other reference. The Mac provides several ways to do this right from your keyboard. Hit the following keys together to capture screen images:

Note: the Command (CMD) key is also known as the Apple key

CMD-SHIFT-3   Saves a copy of the whole screen to the desktop

CMD-SHIFT-4    Cursor changes to cross hairs, allows you to outline a region to capture

Both these capabilities have long been part of the Mac OS. OS X also has the ability to cleanly capture a picture of a single window without the screen background or other annoyances:

CMD-SHIFT-4   Cursor changes to cross hairs, then hit the SPACEBAR
SPACEBAR   Cursor changes to a camera, move over the desired window and click the mouse to save picture

Try it and see what happens. I find this very handy to send pictures of error messages to tech support reps and for clients to send screenshots to me when they have problems.