DNS records: what each type does and which you need

DNS is the phone book that turns a name into an address. Each record type answers a different question about your domain.

The ones you will use

A - points a name at an IPv4 address. This is what makes yourdomain.com reach your server. You need one.

AAAA - the same thing for IPv6. Add it if your server has an IPv6 address.

CNAME - points a name at another name rather than an address. Used for subdomains that should follow something else, most commonly www pointing at the root domain, so that changing the server's IP only means editing one record. A CNAME cannot exist on the root domain itself alongside other records.

MX - says which server receives mail for the domain. Has a priority number; the lowest is tried first. If your mail is not on the same server as your website, this is the record that says so.

TXT - free-form text, used for verification and for mail authentication. Your SPF, DKIM and DMARC records are all TXT records.

The ones you probably will not

NS - delegates a subdomain to different nameservers. SRV - locates a service on a port, used by some VoIP and chat systems. CAA - restricts which certificate authorities may issue certificates for your domain; worth adding if you are being thorough.

TTL

Every record has a Time To Live in seconds, which tells resolvers how long to cache the answer. A high TTL means faster lookups and slower changes. Before you plan a change, lower the TTL to 300 and wait for the old TTL to expire - then the change itself takes minutes instead of a day. Put it back up afterwards.

Where to edit them

In cPanel under Zone Editor, if your domain uses our nameservers. If it uses someone else's nameservers, edit them there instead - records added in cPanel are ignored, which is the single most common reason a change "does not work".

Checking your work

Use dig yourdomain.com MX on Mac or Linux, or nslookup -type=MX yourdomain.com on Windows. That asks DNS directly and skips every layer of caching in between.