nslookup is a network troubleshooting tool in Unix and Linux, it helps resolving IP addresses into hostnames and hostnames into IP addresses by making DNS (Domain Name System) queries.
Why is it called nslookup?
DNS system of the Internet runs with the help of a core component: hundreds of thousands of name resolution servers. They're called NS servers – Name Servers. Recently they're also called DNS servers (Domain Name Servers).
nslookup got its name because it makes queries specifically against NS servers in order to obtain information.
Non-Interactive Use of nslookup
Simply enter nslookup command name followed by a hostname of any website you know:
[email protected]:~ $ nslookup www.google.com
The Non-authoritative answer section contains IP addresses that point to www.google.com in your region.