Reference
DNS record types
What each record does, what its fields mean, and the thing that actually goes wrong with it.
SOA — Start of Authority
The SOA record marks the top of a DNS zone and holds the settings that govern how the zone is copied between nameservers and how long negative answers are cached.
MX — Mail Exchanger
An MX record says which servers accept mail for a domain, and in what order senders should try them.
CNAME — Canonical Name
A CNAME record makes one name an alias for another, so every lookup of the alias continues at the target.
A — Address
An A record maps a hostname to an IPv4 address. AAAA does the same for IPv6.
TXT — Text
A TXT record holds free-form text, and in practice carries SPF, DKIM, DMARC and domain-ownership verification.
NS — Name Server
NS records name the servers that are authoritative for a zone.
PTR — Pointer
A PTR record maps an IP address back to a hostname — the reverse of an A record.
CAA — Certification Authority Authorization
A CAA record names which certificate authorities are allowed to issue certificates for a domain.