What is DNS

DNS (Domain Names Services) is the system that maps a host name (such as a web server) to an IP address.

An IP address is a unique address on a network. In the case of a publicly accessible server, the IP address is referred to as a public IP address and must be issued by an ISP. There are also a number of ranges that are reserved for private networks.

Every server must have at least one IP address, but a server can be known by multiple names. These names can be mapped to an alias, known as a CNAME, or to a specific IP address, called an A record. Good practice usually means that only the primary server name is mapped to an IP address, and all other names use that primary server name as an alias. This means you only have to change it's IP address in one place.

Because of the way DNS works, a root domain can also have an IP address, which means that you can enter a web site address without using www in front of it (e.g. http://bbc.co.uk/ which then redirects you to http://www.bbc.co.uk/)