Apple’s MacBooks and MacBook Pros are built with a solid-state scrolling trackpad. Moving one finger on the trackpad will move the cursor on the screen. The trackpad supports two-finger scrolling when two fingers are applied to the trackpad in a window where scrolling is an option.
One additional feature of Mac OS X with the use of the trackpad is the ability to zoom into one part of the item(s) on your screen, for example, zooming into read some fine print. While holding the control key on the keyboard, move up with two fingers on the trackpad and the display will zoom onto the cursor. To zoom out, hold control and move down with two fingers on the trackpad.
http://docs.info.apple.com/article.html?artnum=300777 http://www.apple.com/education/solutions/macbook/
One more thing – if you’re on a desktop machine (eMac, iMac, or PowerMac/Mac Pro) the zoom in feature can be activated by holding down the control key on the keyboard and scrolling up on the scroll ball on the mouse. To zoom out, hold control and scroll down.