What is purpose of Win Server

Is windows server an operating system for servers or is it a OS for workstations too?

Is it even an OS? I know this sounds dumb and I should know this but I've been at Microsoft.com and could not tell much.

Yesterday I was at a flee market and there was a guy who asked for win server and the vendor told him he has a copy that is designed for 25 users; what does that mean.

My hypothesis is that win server is OS that is located on server and workstations can boot from it, is that correct?

thanks!

It is an OS that was designed to be a server OS. I happen to know some people that use it for their desktop OS, so you can't really say it is only for servers.

My hypothesis is that win server is OS that is located on server and workstations can boot from it, is that correct?

Well workstations don't really boot from it. They boot normally, but they log into a domain that is run by the server.

Say I load a game onto a server with win server OS, can I boot that game from all computers that are connected to that server considering that the game is designed to be ran only one copy on one computer?

No you can't Windows Server Operates in the same way as windows 2000/xp the differences are it's license and I think there are some OS componants only available with windows server.