This tool performs a reverse DNS lookup. In other words, given an IP address, it finds out the associated domain names.
For a given IP address, a reverse DNS record may not always be found. In addition, the domain name found through an a reverse DNS lookup may not lead back to the same IP address.
Technically, reverse DNS lookups are performed by looking up PTR records for the IP.
For performing other kinds of DNS lookups (such as A records or AAAA records), please use the DNS lookup tool.