Domain Name System is the “phonebook of the Internet”. It associates domain names with ip addresses.

The unique perk of DNS is the ability to set up a distributed service. Users refer to the nearest DNS server, so different users can receive different resolutions for the same domain name.

The servers involved in resolving the domain name:

1. DNS recursor (for example, ISP)
2. Root nameserver
3. TLD nameserver (it hosts the last portion of the hostname)
4. Authoritative nameserver

Nodes contain caches, so it's not always necessary to contact the authorative nameserver.