Resource Records(RR) are information entries in the Domain NameSystem( DNS) and in a zone file for the administration of a domain. Resource Records have a fixed structure: "Domain (NAME) - Class( CLASS) - Type (TYPE) - Record (RDATA)".
In the RR structure, Start of Authority Resource Record( SOA-RR) belongs to the RR types. SOA-RR is contained only once in a zone file and that is at the beginning of the "Type" structure area. The Name Server Resource Record( NS-RR) also belongs to the RR types and can be present several times, namely for the different name servers (NS). Other important resource records are the MX record for the name of the mail server, the PTR record for the IP address, the A record for the IPv4 address and the AAAA record for the IPv6 address. These two records are set in the zone file when dual stacking from IPv4 to IPv6. Dual stack is the migration concept for the transition from the IPv4 protocol to the IPv6 protocol, where both IP protocols work in parallel and are supported by all network nodes.
In addition to the RR types mentioned, there are various others for the IP addresses of the hosts, for certificates, complete domain names, for encryption procedures, information about the host, mailboxes, for switching and forwarding and of mails, for access points in the network, for digital certificates and many more.
To make resource records globally readable, several RFCs specify syntax rules for RR types. These rules include that no blank lines are allowed to describe RR types, that comments are indicated by quotation marks, or that longer resource records are enclosed in brackets.