The program doesn't have its own interface, but rather opens up directly in the browser on your PC, which you can configure. You just have to select which type of search you want to perform, and the program will connect you with the Whois database, and display the results.
If you're looking for a domain name that turns out to be registered already, AddInternet will show you all the available options so you can register one if you want to.
On the other hand, if you are looking for information on the domain itself, all you have to do is enter the URL and within a matter of a few seconds the program will display all the related information--owner of the domain, the administrator, and the contact person.
AddInternet supports the following domains in its search: .com, .org, .net, .biz, .info, .co.uk, .ws, and many others.