DNS
The internet's phone book - a system that translates human-readable domain names into IP addresses computers can use.
Definition
DNS (Domain Name System) is a hierarchical naming system that maps domain names like example.com to the numeric IP addresses that computers use to identify each other on the network. Every time you visit a website, a DNS lookup happens in the background before your browser can connect.
Why it matters
Without DNS, you’d need to memorize IP addresses like 142.250.80.46 instead of typing google.com. DNS is also critical infrastructure: misconfigured DNS records can take a site offline, and DNS propagation delays affect how quickly changes reach users worldwide.
Example
When you type a URL into your browser, it queries a DNS resolver (often your ISP’s or a public one like 1.1.1.1) which returns the IP address of the destination server. Email delivery also depends on DNS – MX records tell other servers where to deliver mail for your domain.