Newer Macs, both portable and desktop, come with keyboards that have shortcut keys on the top row, where the F keys are. These F keys allow you to increase or decrease the brightness of the display, control iTunes playback, and raise and lower the volume.
You may also know that these features have associated preference panes in System Preferences as well. You can find them by opening System Preferences, which can be found in the Applications folder. Then you can click on the specific Preference pane you need, like the one for brightness or Mission Control. There’s also a way to get directly to these preference panes with a keyboard shortcut.