Server as Physical Hardware
When we say Server, and we are talking about hardware, we are talking about a computer system that is dedicated to provide services on our network. Those computers could be used as ordinary workstations, but we usually reserve servers to provide services to other systems. To fully understand this we have to know the difference between a Peer-to-Peer network and a Client-Server network. In Peer-to-Peer networks there are no dedicated servers. In Client-Server networks we have a special computer which has some special hardware, and we call that computer a Server.
A server is a computer program that provides services to other computer programs (and their users) in the same or other computers. The computer that a server program runs in is also frequently referred to as a server. That machine may be a dedicated server or used for other purposes as well.
Many types of servers exist, including web servers, mail servers, and file servers. Each type runs software specific to the purpose of the server. For example, a Web server may run Apache HTTP Server or Microsoft IIS, which both provide access to websites over the Internet. A mail server may run a program like Exim or iMail, which provides SMTP services for sending and receiving email. A file server might use Samba or the operating system’s built-in file sharing services to share files over a network.
While server software is specific to the type of server, the hardware is not as important.