Domain Name System (DNS) is a decentralized search service that translates a human-readable domain name or URL into the IP address of the server hosting the website or service. This characteristic of the worldwide distribution of DNS is an important component of the Internet. DNS has been used since 1985.

A DNS server serves two purposes. The first is to maintain a cache that contains domain names that were recently searched for, which improves performance and reduces network traffic. The second is to act as the start of authority (SOA) for all related domains. When a DNS server tries to resolve a domain name that is not in its cache, it starts at the top level (the period) and then works its way through the subdomains until it finds the DNS server that is acting as the SOA. As soon as this is found, the IP address of the domain is stored in its local cache.

The DNS also contains certain entries related to the domain. These records include Start of Authority (SOA), IP addressing (A and AAAA), SMTP email (MX), name server (NS), and CNAME (domain name alias) records.