DNS (Domain Name System)

DNS (Domain Name System) is the distributed, hierarchical system that translates human-readable domain names (like example.com) into IP addresses so machines can locate each other. It is organized into layers (root servers, TLD servers, authoritative name servers) and uses record types such as A, AAAA, CNAME, MX and TXT to store different information about a domain. Recursive resolvers cache responses with a TTL to speed up lookups, which can introduce propagation delay; security extensions like DNSSEC help prevent certain kinds of tampering.

Suppose you run a website on a server with IP 203.0.113.10 and want example.com to point there: you create an A record in your DNS management that ties example.com to 203.0.113.10. For the www subdomain you might create a CNAME that points to example.com, and for email you configure an MX record pointing to your mail server. When obtaining a TLS certificate via Let's Encrypt you may add a temporary TXT record for domain validation; changes can take minutes to hours to propagate because of caching and TTL, so verify updates with tools like dig or nslookup.