Domain Name System (DNS)
The function of a Domain Name System (DNS) is simply to translate domain names into IP addresses and vice versa. Domain names are alphabetic and therefore easier for humans to remember. The Internet, however, is based on IP addresses, where every computer (host) is assigned a unique IP address. Every time you use a domain name, a DNS service must translate the name into the corresponding, machine-friendly IP address and directs your Internet connection to the correct host.
If one of the DNS servers does not know how to translate (resolve) a particular domain name, it asks another one higher in the DNS hierarchy, until the correct IP address is returned from an authoritative DNS server.
After you have registered a new domain or updated the DNS servers responsible for your domain name, it usually takes about 24 to 48 hours for the domain name server hierarchy to be updated (propagate) worldwide and for the information to be accessible. This 24 to 48 hour period is referred to as domain propagation.