At the command window, it displays the username and domain for the currently logged in user.
The whoami output is the same as the 2 environment variables “USERDOMAIN” and “USERNAME”.  So, the same output could be achieved with the following command:
ECHO %USERDOMAIN% %USERNAME%
Under Windows 2000 there is an additional switch WHOAMI /all – this shows all permissions and group memberships.
There are several WHOAMI Internet services available which provides user IP information. Just search for WHOAMI on any search engine on the Internet.