Dictionary
DNS
The system that translates a domain name into the server address a browser can actually connect to.
In more detail
What It Means
DNS, the Domain Name System, is the internet's phone book. It turns a domain like webpageanatomy.com into a numeric IP address, which is the actual address a browser needs to open a connection. This lookup is the first thing that happens before any page can load.
See it in context on the homepage: How a Page Loads.