"Whois" is a service to query the domain registration database globally to find out the owner profile of domain, including register, domain registar, DNS server and many more. Whois is one of the most popular domain tool used by webmasters.
"Whois" a special type of web server used to query the owner, registar, DNS server of domain. Whois is helpful to find the ownership a domain.
What's Domain Privacy
Domain Privacy feature of a domain will hide domain owner of a domain, instead, system will show the common information of domain registar only. Domain Privacy is an advanced feature of domain, and normally your domain registar will charge you some to offer this service.