A server is a special computer, a device or a program that is dedicated to managing network resources. Servers are often referred to as dedicated because they carry out hardly any other tasks apart from their server tasks.
Types of server
Exchange Server (Mail Server)
In the client/server model, a file server is a computer responsible for the central storage and management of data files so that other computers on the same network can access the files.
A file server allows users to share information over a network without having to physically transfer files by floppy diskette or some other external storage device. Any computer can be configured to be a host and act as a file server.
Mail Server (Email Server)
A mail server (also known as a mail transfer agent or MTA, a mail transport agent, a mail router or an Internet mailer) is an application that receives incoming e-mail from local users (people within the same domain) and remote senders and forwards outgoing e-mail for delivery.
A computer dedicated to running such applications is also called a mail server. Common mail server programs are as below.