Every website has a specific and unique IP address, however remembering each individual IP address can be a painful experience and a misprint of a number leads to a completely different website. Instead, we have domain names which provide a much more human-friendly approach, which maps a string of letters and numbers to a direct IP address.
For example, the popular social media website, Facebook, has a domain name www.facebook.com instead of its long IP address (184.108.40.206). No-one would want to use Facebook if it didn’t have a domain name.
The infrastructure that allows us to register these domain names to a specific IP address is through a DNS server. Your internet provider would have its own DNS where it can potentially filter out specific IP addresses such as torrenting websites.
Therefore, the DNS essentially works like a yellow pages or white pages. You type in the domain name, your browser connects to the DNS server which matches up the domain name with the correct IP address and then you are presented with the correct website.This all happens in the matter of milliseconds!
This is just the tip of the iceberg, for a more indepth look at DNS and DNS resolutions, I would recommend looking at http://computer.howstuffworks.com/dns.htm