DNS
also: Domain Name System, name resolution, DNS lookup
DNS (Domain Name System) is a distributed network service that translates human-readable domain names into IP addresses, enabling computers to locate each other on the internet.
DNS operates like a phonebook for the internet. Instead of remembering that google.com is located at 142.250.185.46, your browser queries DNS servers to resolve the domain name to its corresponding IP address.
When you enter a URL in your browser, your system contacts a DNS resolver (often your ISP's server or a public one like 8.8.8.8) which queries a hierarchy of nameservers: root nameservers, top-level domain (TLD) servers, and authoritative nameservers. Each level narrows down the search until the IP address is returned.
On Linux, DNS resolution is configured through files like /etc/resolv.conf or managed by tools like systemd-resolved. You can test DNS with commands like nslookup example.com or dig example.com to see what IP address a domain resolves to.