A domain is a name you rent. DNS is the phone book that turns that name into the address of a machine. That's it — the rest is vocabulary.

Buying one

Buy from a registrar that sells domains and doesn't upsell you eleven other things: Cloudflare, Porkbun and Namecheap are all fine. Expect £8–15 a year for a .com. Ignore the first-year-99p deals with a £40 renewal.

Turn on WHOIS privacy — it's usually free and keeps your home address out of a public database. Turn on auto-renew, because the single most common way people lose a domain is forgetting to pay for it.

The four records you'll meet

  • A — points a name at an IP address. example.com → 203.0.113.5
  • CNAME — points a name at another name. www.example.com → myapp.netlify.app
  • MX — where email for this domain goes.
  • TXT — free-form text, used to prove you own the domain and to configure email (SPF, DKIM, DMARC).

Your host will tell you which to add. You add it at your registrar.

Why it isn't working yet

Nearly always one of three things: you added the record at the wrong place (registrar vs host), you included the domain in the "name" field when it wanted just www, or it has worked for ten minutes and your computer is still remembering the old answer.

dns-help.txt
My domain is at <registrar>. My site is hosted at <host>, which told
me to add: <paste their instructions>.

Tell me exactly what to type in each field. My registrar's form has
fields for <list them>. Say whether the name field wants "@", "www",
or the full domain.

Then: how do I check it worked, from a terminal, without waiting?

dig example.com or nslookup example.com shows you what the world sees, which is usually different from what your browser is showing you.

Changes propagate in minutes to hours, not days, despite what the internet says. If it's been an hour and nothing has changed, the record is wrong — waiting longer won't fix it.

HTTPS

Free and automatic on every modern host. If yours makes you buy a certificate or configure one by hand, that's a reason to change host, not a reason to learn about certificates.