Also known as a pointer record is a type of DNS entry or resource record used to resolve an IP address into a domain name, precisely the opposite of an A record, which provides the IP address associated with a domain name.
So, a PTR record ensures that your IP address officially connects to your host.
PTR record is called a reverse DNS entry as it is used for reverse DNS lookups. When a user accesses a domain name in their browser, a DNS lookup happens, matching the domain name to the IP address. A reverse DNS lookup is the opposite of this process – a query that starts with the IP address and looks up the domain name.
An A record exists for every PTR record.