What is private domain registration ?

All domain name owners must include contact information in their domain name record, however, you don't have to make this information public.

Yahoo! Private Domain Registration allows you to conceal personal information from unwanted solicitors by listing contact information for Yahoo!' domain name registration partner Melbourne IT, in place of your own registration, administrative, technical, and billing contact information in the public WHOIS database . Your own contact information will remain associated with your domain in the public yahoo !/

Melbourne IT's database but will not be made available in the public WHOIS.