DNS is an acronym for Domain Name Server. This server maps IP addresses to host names. This allows computers to be accessed remotely by name instead of number.
When you type in "www.everything2.com" into your web browser, your computer first checks to see if it knows the IP Address (usually in memory, or on the computers DNS server). If it doesn't (usually), then it makes a request to the local DNS on your network. This server then replies with the IP Address of the computer you are looking for.
If your local DNS doesn't have the IP Address for "www" at "everything2.com", it will make a request to the DNS at "everything2.com", which will give it the IP Address of "www", which will then be forwarded to you. Happy!