All of the various internet activities, such as sending and receiving email, are performed by specific, dedicated computers called "servers." In order for a computer to send or receive an email, or reach a website, it first has to find the server responsible for that function. That is what DNS is for.

All machines on the internet are found and identified by specific addresses which are signified by a series of numbers separated by dots, like 192.168.24.5. This kind of server address is called an "IP address". However, just using the IP address to locate a server or website on the internet can be problematic. First of all, a website address like "198.168.24.5" is a lot more difficult to remember than an address like "example.com." And if the IP address of the website ever needs to change then you have to be concerned with having people find out about the change, and remembering a whole new confusing address.

So, in order to create a constant, fixed internet address that is easy to record and remember, and works even if the server's numeric IP address changes, we use domain names to represent the IP addresses of servers that perform any internet related activity.

The purpose of DNS is to convert the names to the numbers so that the appropriate servers can be found, very much like a phone directory or an address book.