DNS record types

SOA - Source Of Authority. Defines the owner of a domain, as well as how long a record for the given domain may be cached by other DNS servers.
NS - Name Server. Who are the authoritative name servers for a given domain.
A - Address. What is the IP address of a given host.
PTR - What is the host name attached to a given IP address.
MX - Mail eXchange. Which host serves as the mail exchange for a given host or domain.
CNAME - Canonical Name. Defines alternative "nicknames" for a given host.