Servers are essentially beefed up computers that have specialized server operating system.
"Beefed up" usually includes a better power supply and often a motherboard that is more suited to calculations and often will hold more memory.
Server software has the ability to create a domain. This will allow all of the computers to connect to each other. Peer to Peer is limited to a maximum of 10 computers, I believe, domains have no such restrictions.
With a domain the server can make sure that all computers have the same set of administrative restrictions and controls. It can also push through updates automatically.
Servers usually have the role of "serving" information or serving as a central repository. While a regular computer can do this, Microsoft server software has a beefed up version of SQL server that will allow you both more control and handle more simultaneous requests for information.
Servers often control your internet access and can enforce both global restrictions as well as host web pages for the external world.
They can house an internal website to make access of information easier.
They can house an external or internal webmail system that gives you lots of options on both how you control your flow of email and how it is scanned for viruses.
They can house virtual machines which act as separate computers and isolate the main system from things run by the virtual machine.
Servers can also back up the other machines, but selectively and globally.
They can do more, but these are the things that come to mind.
While many of these things can be done on individual computer and a variety of software, some are exclusive to servers and specifically microsoft servers, (there is a lot of free linux servers that can do domains, email and back up stuff) all of these things are together in a single package (there are a lot of different MS packages as well) and integrate with windows software well.
Bert needs to chime in now, as he knows far more than I when it comes to servers. I currently run peer to peer
but servers are a good idea.
