What each record type means
- A
- The IPv4 address a name points to. This is usually where the website is served from.
- AAAA
- The same thing for an IPv6 address.
- CNAME
- An alias to another name. A name that has a CNAME cannot hold any other record.
- MX
- The hosts that receive mail for the domain. The lower preference number is tried first.
- NS
- The name servers responsible for the zone. The delegation itself is set at the registry.
- TXT
- Free text. SPF, DKIM, DMARC and service ownership strings all live here.
- SOA
- The start of authority record, with the zone serial number and the refresh and retry timers.
- CAA
- Says which certificate authorities are allowed to issue certificates for this domain.
TTL, and why a change is not visible straight away
TTL is the number of seconds a resolver is allowed to keep an answer in its cache. If an A record has a TTL of 3600, then for up to an hour after you edit it part of the world still sees the old address. Nothing is broken, that is how DNS caching works.
Before a planned move, lower the TTL to 300 seconds, wait for the old TTL to run out everywhere, and only then change the record. Put the TTL back up once the move is finished.