DNS changes those domain names to the numbers which are assigned to them. Allows you to contact the proper sites by their domain names without needing to know their actual IP address.
If you want to know their IP address, open a command box and ping them. You can also tracert them to see the internet pathway to them.
ping microsoft.com
Coming back the other way.
If you have a router, maybe you see Dynamic DNS available in it? That's to help people find YOU if you run a server. It sends your ISP (internet service provider) assigned IP address (internet protocol) to a DNS service which then binds it on their server to your assigned domain name. That way if you run your own server and your IP address can change from time to time, your domain name when used by others will always still come to your server.
domain names = IP addresses