You can take screenshots of your whole screen or just part of it. Screenshots are saved automatically as .png files on your desktop.

Take a screenshot of your whole screen

1. Press Command (⌘)-Shift-3.
2. Screenshot is saves as .png file on your desktop.

Take a screenshot of part of your screen

1. Press Command (⌘)-Shift-4. The cursor changes to a crosshair pointer.
2. Move the crosshair pointer to where you want to start the screenshot.
3. Drag to select an area. To adjust the area, hold Shift, Option, or the Space bar while you drag.
   
4. When you've selected the area you want, release your mouse or trackpad button. Or to cancel, press Escape (esc).
5. Screenshot is saves as .png file on your desktop.