Reverse parsing of iquery and PTR queries

At first, I did not consider reverse parsing rather than PTR. Later I mentioned these two concepts when I read a technical document, but there is no clear difference.

Later I made some research:

1. ptr resolves an IP address to a domain name. ptr-type queries are also standard queries. The question field is queried as 1 and then the Server gives the answer, the server will put the query result in answer and other fields and return it to the client;

2. for reverse query, the answer field of the request packet is not empty, the question field is empty, and the response packet returned by the server is placed in the question field, therefore, the number of resource records in the question field may be greater than 1.

Reverse query can also resolve the domain name corresponding to the IP address, but it should have more functions, not just the resolution of the IP address to the domain name. Further research is required.