Windows Server 2003 installation and requirements

I tried Microsoft website to find answers to my questions but to no
avail.
1 - After installation, is Windows Server 2003 an operating system on
its own?
2 - If so, is it much like XP Professional where one can also use it as
a regular home PC?
3 - Does it need XP Professional installed on the PC as a prerequisit
to its own installation?
I ask these questions because I just bought Visual Studio 2005
Professional and I see that XP Pro and Windows Server 2003 were
included.

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