What is DNS?
DNS, or Domain Name System, is the telephone book behind the scenes, ensuring you get to Google when you type www.google.com into your browser. DNS eliminates the need for us to remember things like IP addresses when we want to get to our favorite websites.
Imagine, you want to visit Engadget. Sure, you can bookmark the website by it's IP address: 126.96.36.199, but you won't be able to load the website by just typing that in your browser, and what if the IP address changes.
It would be like the old days when there were paperback cable guides mailed to our homes each week, except you would need to send a new "Internet IP address directory" every few weeks, if not every month. The amount of time it would take to properly catalog and ID each IP address, and ensure every website loaded from that IP address reliably, then compiling it into a directory, printing and mailing it.... there's more logistics to it than just those few things, as well.
In the early days of the ARPANET, that's actually how it was done! Except, the directory wasn't but a few pages.