A Reverse DNS is usually a premium feature inside a paid managed DNS plan. It is a service that is mostly directed towards IP network owners and offers IP address to domain resolving. Other business owners might also be interested in it because that way, their emails have a better chance of not going to the spam folder.
Reverse DNS explained
Reverse DNS, also known as rDNS, does the opposite to a Forward DNS, which is to map IP addresses to hostnames. The purpose of the Reverse DNS is to provide a way to verify the IP addresses and confirm that they are related to a particular domain name. It is especially important when we are talking about the verification of mail servers or other services.
If you can’t verify, it is safer to mark it as dangerous, and this is what many servers could do if there is not Reverse DNS zone to be checked.
In short:
In Forward DNS, a domain name is pointing to an IP address where it is hosted.
In Revere DNS, An IP address is pointing to a domain name to verify it belongs to it.