namebench looks for the fastest DNS (Domain Name System) servers accessible
to your computer. You can think of a DNS server as a phone book:
When you want to dial a company on the phone, you may have to flip through a
phone book by name to find their phone number. On the internet,
when you want to visit "www.google.com", a DNS server needs to looks up
the correct IP Address for you.
Over the course of loading a single web page, your computer may need to look up
a dozen of these addresses. While your internet provider usually automatically
assigns you one of their servers to handle looking up these addresses, there
may be others that are significantly faster.