KEY : Key record (RFC 4034)
Used only for TKEY (RFC 2930). Before RFC 3755 was published, this was also used for DNSSEC, but DNSSEC now uses DNSKEY.

TXT : Text record (RFC 1035)
Originally for arbitrary human-readable text in a DNS record. Since the early 1990s, however, this record more often carries machine-readable data, such as specified by RFC 1464, opportunistic encryption, Sender Policy Framework, DomainKeys, DNS-SD, etc.

TKEY : Transaction Key (RFC 2930)
One way of providing a key to be used with TSIG

TA : DNSSEC Trust Authorities (None)
Part of a deployment proposal for DNSSEC without a signed DNS root. See the IANA database and Weiler Spec] for details. Uses the same format as the DS record.

LOC : Location record (RFC 1876)
Specifies a geographical location associated with a domain name

SOA : start of authority record (RFC 1035)
Specifies authoritative information about a DNS zone, including the primary name server, the email of the domain administrator, the domain serial number, and several timers relating to refreshing the zone.

SPF : SPF record (RFC 4408)
Specified as part of the SPF protocol, as an alternative to storing SPF data in TXT records. Uses the same format as the TXT record.

SIG : Signature (RFC 2535)
Signature record used in SIG(0) (RFC 2931). Until RFC 3755 was published, the SIG record was part of DNSSEC; now RRSIG is used for that.

HIP : Host Identity Protocol (RFC 5205)
Method of separating the end-point identifier and locator roles of IP addresses.

NAPTR : Naming Authority Pointer (RFC 3403)
Allows regular expression based rewriting of domain names which can then be used as URIs, further domain names to lookups, etc.

NSEC3 : NSEC record version 3 (RFC 5155)
An extension to DNSSEC that allows proof of nonexistence for a name without permitting zonewalking

A : address record (RFC 1035)
Returns a 32-bit IPv4 address, most commonly used to map hostnames to an IP address of the host, but also used for DNSBLs, storing subnet masks in RFC 1101, etc.

* : All cached records (RFC 1035)
Returns all records of all types known to the name server. If the name server does not have any information on the name, the request will be forwarded on. The records returned may not be complete. For example, if there is both an A and an MX for a name, but the name server has only the A record cached, only the A record will be returned.

CERT : Certificate record (RFC 4398)
Stores PKIX, SPKI, PGP, etc.

AFSDB : AFS database record (RFC 1183)
Location of database servers of an AFS cell. This record is commonly used by AFS clients to contact AFS cells outside their local domain. A subtype of this record is used by the obsolete DCE/DFS file system.

DHCID : DHCP identifier (RFC 4701)
Used in conjunction with the FQDN option to DHCP

IXFR : Incremental Zone Transfer (RFC 1995)
Requests a zone transfer of the given zone but only differences from a previous serial number. This request may be ignored and a full (AXFR) sent in response if the authoritative server is unable to fulfill the request due to configuration or lack of required deltas.

NS : name server record (RFC 1035)
Delegates a DNS zone to use the given authoritative name servers