Every machine on a network has a unique identifier. Just as you would address a letter to send in the post, computers use the unique identifier to send data to specific computers on a network. Most networks today, including all computers on the Internet, use the TCP/IP protocol as the standard for how to communicate on the network. In the TCP/IP protocol, the unique identifier for a computer is called its IP address.
There are two standards for IP addresses: IP Version 4 (IPv4) and IP Version 6 (IPv6). All computers with IP addresses have an IPv4 address, and many are starting to use the new IPv6 address system as well. IPv4 addresses consist of four eight bit numbers (octets), such as 22.214.171.124. To allow many computers to be addressed, there will often be more than one IP address. Computers on a LAN may each have a private IP address, whereas the router through which they connect to the internet has its own public IP address.
Routers make use of IP addresses in order to deliver data to the right place. Humans are not very good at remembering sets of numbers, so many of the resources on the internet are given easily remembered names, such as cssouth.uk. Domain Name System (DNS) servers translate the names into IP addresses.
DNS is a protocol within the set of standards for how computers exchange data on the Internet and on many private networks, known as the TCP/IP protocol suite. Its basic job is to turn a user-friendly domain name like "lloydsbank.co.ik" into an Internet Protocol (IP) address like 126.96.36.199 that computers use to identify each other on the network. It's like your computer's GPS for the Internet.
Computers and other network devices on the Internet use an IP address to route your request to the site you're trying to reach. This is similar to dialing a phone number to connect to the person you're trying to call. Thanks to DNS, though, you don't have to keep your own address book of IP addresses. Instead, you just connect through a domain name server, also called a DNS server or name server, which manages a massive database that maps domain names to IP addresses.