server vs desktop

[userfriendly]

You can also look at its function.

Server - it gives out different kinds of services to the client.
Desktop - the one that connects to the server. It can also be stand alone wherein all the interface needed by the user are there.

So you mean, if you configure a desktop to throw out data to other pcs, then in effect its acting as a server.

When does one need to use a high end server instead of a desktop acting like a server? I imagine its when your running mission critical programs like a huge database or a point of sale system for a big supermarket or department store. Is this correct?

Also, I heard there is such a thing called "dumb terminals". From what I gather, its a pc without a hard drive or something like it. When is this used and will you need a server to feed it data?