For example, to look up the IP address of www.yahoo.com, use nslookup www.yahoo.com:
Server: resolver1.opendns.com
Address: 208.67.222.222
Non-authoritative answer:
Name: fd-fp3.wg1.b.yahoo.com
Addresses: 2001:4998:c:a06::2:4008
206.190.36.105
206.190.36.45
Aliases: www.yahoo.com
You can also specific the DNS server to use: nslookup www.yahoo.com 8.8.8.8
Server: google-public-dns-a.google.com
Address: 8.8.8.8
Non-authoritative answer:
Name: fd-fp3.wg1.b.yahoo.com
Addresses: 2001:4998:c:a06::2:4008
206.190.36.45
206.190.36.105
Aliases: www.yahoo.com
Finally, you can also use the debug option for addition outputs. I.e., nslookup -debug www.yahoo.com 8.8.8.8