The Domain Name System (DNS) translates human-readable domain names into IP addresses that computers use to communicate, serving as the internet's directory service. Operating through a globally distributed hierarchy of servers—from root servers through TLDs to authoritative nameservers—DNS enables virtually every internet interaction. Understanding DNS record types, zone management, resolution flows, security mechanisms like DNSSEC, and troubleshooting techniques is essential for network administrators, security professionals, and developers building resilient internet infrastructure. DNS performance, caching behavior, and attack surface remain critical concerns as the protocol continues evolving with privacy enhancements and security extensions.