The whois utility is a unix or dos utility which tells you useful information about a particular domain. It is used to check if a domain is available. If a domain is not available, it will provide information when the domain was registered, when it expires, who it is registered through, etc.
The reason for adding a utility for whois? Many company firewalls prevent the whois utility from running. This way it is unobstructed and will run through a browser.