The records you will actually meet
- A record: points the domain (or www) at a server's IP address. This is 'where the website is'.
- CNAME record: points a name at another name, for example www to your host's address, or a subdomain to Shopify.
- MX record: says which mail server receives email for the domain. Wrong MX records mean lost email.
- TXT record: free text used to prove ownership (Google Search Console, Microsoft 365) and to authorize senders (SPF, DKIM, DMARC) so your email does not land in spam.
- Nameservers: the setting that says which company holds all the records above. Changing nameservers moves the whole DNS to a new provider.
When you will touch DNS
Launching a new site (point the A or CNAME record at the new host), moving hosts, setting up business email, adding email authentication so invoices stop going to spam, verifying ownership with Google, and putting a CDN or firewall such as Cloudflare in front of the site. Each of these is a one-line change at the registrar or DNS provider, and each one, done wrong, can take your site or email offline. Write down what the records were before you change them.
Propagation, and why changes seem slow
Every DNS record has a 'time to live' that tells the world how long to remember it. Until that time passes, some visitors see the old record and some the new. Most changes are visible within an hour; a few can take a day or two for everyone. Lowering the TTL a day before a planned move makes the switch faster. If a site is 'up for me but down for a client' right after a change, that is propagation, not a broken site.