Why is WhoisGuard necessary?
When you register a domain, ICANN requires domain registrars to provide them with your contact information (such as name, email, address, and phone number). This is then added to the Whois database. This database lists the owners of every domain name online, and it can be searched by anyone on the Internet.
If you have WhoisGuard protection then it hides this (such as name, email, address, and phone number) information from spammers, marketing firms, and online fraudsters. Instead, the Whois database will display generic WhoisGuard contact information.