That means you can completely customize the keyboard on your Mac so the keys function the way you want.
All you need is the free app KeyRemap4MacBook. That’s a mouthful and as descriptive an app name as you’ll likely ever have. What it does is useful because you control the keys on the Mac’s keyboard by completely remapping them to fit your needs.
How it gets there is a bit more complicated. One by one you can change the keys on the keyboard to performa different function.
While KeyRemap4MacBook is powerful, it’s also complex to setup. Click the Change Key tab to change each key and remap it to another function.
You can also control key repeat rate, have the remapped keys visible with a click in the Menubar, and uninstall KeyRemap4MacBook and go back to the default Mac settings for your language keyboard.
The manual walks through the basic steps to install KeyRemap4MacBook, and how to remap keys using the Preference Pane.
The app is oddly named because it actually works on most modern Macs, not just the MacBooks.