DNS, the Domain Name System, is the internet's directory for domain names. When someone types your web address or sends you an email, their device asks DNS where that name's website or email is handled, and DNS answers from records that whoever controls your domain has set.
How it works
Every domain has a set of DNS records, held on its nameservers. Each record answers one particular question:
- An A record gives the address of the server hosting the website.
- A CNAME record says one name is an alias of another, often used for www.
- An MX record says which servers receive the domain's email.
- TXT records hold short pieces of text, mostly used to prove ownership of the domain and to authenticate email (SPF, DKIM and DMARC).
Answers are cached by servers around the world for a set time, the TTL, which is why a change can take a while to be seen everywhere.
Why it matters to a business
Whoever can edit your DNS can send your website visitors and your email anywhere they like. The login belongs with the business, not with whoever happened to set the site up.
It is also where most website-move mistakes happen. Website and email are controlled by different records, so a move goes smoothly when only the right ones are changed. Can I move my website without moving my email? shows which.