Miscellaneous Things You Need to Know About Macs
You can capture screens on your Mac.
Maybe you want to take a picture of the screen for a presentation at work. Or perhaps you want to show precisely what a funky error looks like to the person who just might help you correct the problem. Regardless of motivation, if you want to grab a picture of the Mac screen (or any of its windows), it may be time to open the Grab utility.
Go to Applications→Utilities and click Grab. Through Grab’s Capture menu, you can take a picture of a full screen, window, or menu.