Network locations in Mac OS X

One of the minor mysteries of OS X - newly explained:

Using network locations in Mac OS X: ...A 'location' is a set of network preferences...

It might have been better if they'd called the tool "custom network preferences", but Locations does have a smoother sound. Most of us rarely need to use anything but Automatic these days, but if you want to experiment with OpenDNS (example: block problem addresses) you can create a custom OpenDNS location.