Hi people i started learning windows server 03 and faced big problems. first of all what exactly is domain controller or something like that,i searched on internet and found scientific answers,i need an example only. and how windows server is used in companies? i mean what are they putting in it or what is the main usage?

Here are two links to brief descriptions of a domain controller: http://en.wikipedia.org/wiki/Domain_controller http://www.webopedia.com/TERM/D/domain_controller.html If you can't understand those, then there's nothing we can say to explain it any better. Those are "basic" descriptions and from there, the explanations only get more technical. Ignore the Windows NT portion of the wikipedia page and just read the Windows 2000 portion.

Normally companies use active directory to create and mange users under a particular domain name. Domain controller is used to manage all security-related aspects between user and domain interactions, centralizing security and administration netandhost.com