Nslookup is a program used to quey Domain Name Servers (DNS). It interactively queries servers running DNS. When a domain is checked in nslookup, a query packet is sent by nslookup to the DNS server.
Nslookup helps for getting information about a host in a network. Nslookup is a program to query Internet domain name servers. Nslookup has two modes: interactive and non-interactive. Interactive mode allows the user to query name servers for information about various hosts and domains or to print a list of hosts in a domain. Non-interactive mode isused to print just the name and requested information for a host or domain.