The internet has long had something called DNS (Domain Name Service), which is basically like a phonebook or directory for the internet. When someone calls you, they can look in the yellow pages using their name and find out what the number is and call it.
So this is exactly what DNS does. When you type in a site address like www.serversuit.com your browser actually refers to the DNS to get the IP address and contact that address. Matching the www. address to the IP address is referred to as "resolving."
On top of that, however, internal networks may be organized differently using an Apache server. When an IP connection comes into the server, the client will specify the name they're looking for, and the server will check the configuration on how to resolve it.
It's pretty straightforward, and it plays a big part in the way servers are set up online.