What is an A record, an NS record, a PTR record, a CNAME record, an MX record?

An NS record is operated to give a subdomain to a set of name servers. Whenever a user delegates a domain to DNSimple, the TLD authorities automatically place NS records for that domain in the TLD name servers. 

The PTR record is basically used as a spam filter and is used to authenticate the incoming messages. An A record should always exist for the PTR records. 

CNAME stands for Canonical Name, which is what this record provides to an alias name. 

MX stands for Mail Exchanger and the MX record is a special type of resource record in the DNS (Domain Name System). It specifies a mail server, which is completely responsible for accepting the messages via email on behalf of the recipient’s domain. A preference value is used to prioritize the mail delivery in case of multiple servers.