Domain Name System (DNS) is a hierarchical and decentralized naming system used to translate human-readable domain names, like en.fasoo.com, into numerical IP addresses, such as 192.0.2.1, which are used by computers to identify and locate each other on the internet. DNS functions like a phone book for the internet, enabling users to access websites and other online resources using easily remembered names rather than complex numeric addresses. It is essential for the functioning of the internet, as it facilitates the routing of traffic and ensures that users can reach the correct destinations efficiently.