A mail exchanger record (MX record) is a type of resource record in the Domain Name System that specifies a mail server responsible for accepting email messages on behalf of a recipient's domain, and a preference value used to prioritize mail delivery if multiple mail servers are available. The set of MX records of a domain name specifies how email should be routed with the Simple Mail Transfer Protocol (SMTP).
An A record (Address Record) points a domain or subdomain to an IP address.
A name server is a computer server that hosts a network service for providing responses to queries against a directory service. It maps a human-recognizable identifier to a system-internal, often numeric identification or addressing component. This service is performed by the server in response to a network service protocol request.
A PTR record is the reverse of an A record. That is, it maps an IP address to a hostname, rather than vice versa.