The
DNS stands for
Domain Name System. It is a mechanism that converts hostnames to IP addresses so that, when you type a website address into your browser, you can quickly identify the right server. Each domain name has one or more "resolvers," or IP addresses, associated with them by the DNS system.
When you enter a URL (such as www.google.com) into the browser, your computer requests the IP address connected with that web address from the DNS resolver. The IP address of a local machine or another server which has been set up to return that specific IP address is then returned to the browser by the DNS resolver.
Consider the below image for a better understanding :
DNS is necessary because hosts on the Internet have only human-readable names like google.com and not machine-readable names like 111.222.333.444. Without DNS, you would need to know how to interpret a URL's human-readable name in order to find it on the Internet, which would be very difficult without a centralized authority like Google to help you out!
