What Is DNS? How a Domain Resolves to a Server

You type example.com and a website appears. But computers don't route traffic by names — they route by IP addresses, numbers like 93.184.216.34. Something has to translate the friendly name into the number, every single time, before your browser can connect. That translator is DNS, the Domain Name System, and it's basically the phone book of the internet.

The problem DNS solves

Humans remember names; networks need numbers. Nobody wants to memorise 93.184.216.34, and the address behind a site can change without warning. DNS is the layer of indirection that lets you keep using a stable name while the number behind it can move.

The lookup journey

When the name isn't already cached, your request hops through a small chain:

1. Your computer asks a resolver (usually your ISP's or something like 1.1.1.1).
2. The resolver asks a root server: "who handles .com?"
3. That points to the .com nameservers: "who handles example.com?"
4. Those point to the domain's authoritative nameserver, which finally answers with the IP.

The resolver caches the answer so the next visit skips the whole trip.

DNS is a series of "I don't know, but I know who does" hand-offs, from the root down to the server that actually owns the record. It usually finishes in milliseconds.

The records you'll actually meet

A domain's DNS is a set of records. The common ones:

• A — maps a name straight to an IPv4 address (the workhorse).
• AAAA — same, but for an IPv6 address.
• CNAME — an alias pointing one name at another name.
• MX — where email for the domain should go.

Why changes aren't instant

Because answers are cached all along that chain, a change (repointing a domain to a new server) doesn't take effect everywhere at once. Each record has a TTL — how long resolvers may cache it — so updates "propagate" as old cached copies expire. That's why a new site can appear for you but not yet for a friend.

The mental model to keep

Picture a chain of directories that turn a name into an address, with copies cached at every step for speed. Your browser can't connect until that lookup returns a number — which is why "the site is down" is sometimes really "DNS is pointing at the wrong place."