$ whatis nslookup

nslookup - query Internet name servers interactively

Examples:

1. nslookup www.mywebuniversity.com
2. nslookup+ourunix.com
3. nslookup -q=mx www.mywebuniversity.com
4. nslookup -q=A www.mywebuniversity.com

Please click on "man nslookup " to see the Manual Page for this command.