What do you mean by forward lookup zone and reverse lookup zone?

There are 2 zones which are required by dns to resolve the query related with the FQDN and IP address.

Forward lookup zone is FQDN(fully qualified domain name) to IP address

Reverse lookup zone is IP address to FQDN(fully qualified domain name)

if you ping or do nslookup it check the dns for the information.

ping abc.Microsoft.com

internally it will check the table and find out what is the Ip address for abc.Microsoft.com then it will show on the cmd prompt

Pinging abc.Microsoft.com [207.46.232.182] with 32 bytes of data:

"forward look-up zone" and "reverse look-up zone" usually refer to domains/zones, or correspondingly to cache or configuration files, in a Domain Name System (DNS).

For instance:

"Answers.Com" represents a "forward look-up zone" and contains Address (A) records, among others, such as:

WIKI.Answers.Com A 67.196.156.63

There is (or at least "should" be) a corresponding "reverse look-up zone", either:

67.in-addr.arpa,

196.67.in-addr.arpa, or

156.196.67.in-addr.arpa

containing (PTR) records, with something like:

63.156.196.67.in-addr.arpa PTR WIKI.Answers.Com

These are used "Behind the Scenes" by the DNS portion of the internet protocol to resolve Names into Internet Protocol Addresses, and to resolve Internet Protocol Addresses into Names.