DNS Record types

A  - Address, code 1. Used for storing an IP address (specifically, an IPv4 32-bit address) associated with a domain name. Defined in RFC 1035.

CNAME  - Canonical name for a DNS alias, code 5. Note that if a domain name has a CNAME record associated with it, then it can not have any other record types. In addition, CNAME records should not point to domain names which themselves have associated CNAME records, so CNAME only provides one layer of indirection. Defined in RFC 1035.

MX  - Mail Exchanger, code 15. Each MX record specifies a domain name (which must have an A record associated with it) and a priority; a list of mail exchangers is then ordered by priority when delivering mail. MX records provide one level of indirection in mapping the domain part of an email address to a list of host names which are meant to receive mail for that domain name. Critical part of the infrastructure used to support SMTP email. Defined in RFC 1035.

NS  - Authoritative name server, code 2. Specifies a host name (which must have an A record associated with it), where DNS information can be found about the domain name to which the NS record is attached. NS records are the basic infrastructure on which DNS is built; they stitch together distributed zone files into a directed graph that can be efficiently searched. Defined in RFC 1035.

PTR  - Domain name pointer, code 12. Provides a general indirection facility for DNS records. Most often used to provide a way to associate a domain name with an IPv4 address in the IN-ADDR.ARPA domain. Defined in RFC 1035.

SOA  - Start of authority, code 6. Marks the start of a zone. Defined in RFC 1035.

TXT  - Text string, code 16. Arbitrary binary data, up to 255 bytes in length. Defined in RFC 1035.