DNS
In plain terms
The system that translates human domain names into machine IP addresses.
Going deeper
The Domain Name System resolves names like example.com into the numeric IP addresses computers use to connect. It's a distributed, hierarchical directory underpinning nearly all internet navigation.
Under the hood
Hierarchical and cached at many layers (resolver, OS, browser) with TTLs; record types and propagation delays trip people up, and DNSSEC adds integrity.
Examples
A, AAAA, CNAME, MX, TXT records; nslookup/dig; Route 53, Cloudflare DNS.
Think of it like...
Like the internet's phone book: you look up a name and it gives you the number to actually place the call.