We are going to be discussing what a server is, as it pertains to the world of computers and computing. In this regard a server is a computer program that works to attend to the needs and demands of other computer programs (these are referred to as clients). Those programs may be operating on a different computer or on the same one as the server program. A server could also be an actual computer, or a group of computers, whose purpose is to run one or more computer programs operating together on the same network.
A computer server can be a combination of both software programs and hardware, such as a file server, mail server, print server or a database server. Each one of these serve different and unique purposes. A good example of this would be when you enter a request in to a search engine, that request is sent from your computer over the net to one or more servers that have the related pages stored on them.
The reply or results are then sent back, by the server program, to your computer. You're likely asking yourself why servers are essential. They're needed so that the Internet runs effectively. If there were no servers saving web pages on them, you could not send out a search, since there would be nothing there for you to look for. This is just the vast public need for servers to be available. Servers also store programs that tell search engines how to work, as well as how web pages are rated so that the system knows what order to transmit the results of a query.
Servers are also needed in the private use of corporations. They hold massive directories of the various types of information that these organizations need to keep and have immediate access to. There could be individual servers for each type of information databases and a server that controls how they are accessed.
It's also the server that permits an organization to have a network of computers connected together to be able to access the data. The networking program is a server program and enables or limits the flow of internal information to only the computing devices with stored access clearance. If servers are so crucial, what goes on when a server stops working? If a server stops working, someone has to determine why and make fixes so it can be taken back online.
Out on the internet there are back-up servers. When one crashes and its information or instructions aren't accessible but the internet will redirect their request and seek the information it needs by using a different server on the network that can do nearly exactly the same thing that the server that crashed does. It is this back-up system (called a redundancy) that keeps the Internet working 24/7/365.
When we're talking about a web server within a company breaking down, it could cause the work being done to come to a decisive stop. Like the servers on the internet, the server must be fixed and brought back online so the corporate network system can get back to work. It is for this very reason that corporations have taken a lesson from the internet and have redundant back up rack server products set up and a program that will instantly switch to the back if the main server goes down.