Types of servers

Servers are often categorized in terms of their purpose. A few examples of the types of servers available are as follows:
web server is a computer program that serves requested HTML pages or files. In this case, a web browser acts as the client.

web server

An application server is a program in a computer in a distributed network that provides the business logic for an application program.
proxy server is software that acts as an intermediary between an endpoint device, such as a computer, and another server from which a user or client is requesting a service.

proxy server

A mail server is an application that receives incoming emails from local users — people within the same domain — and remote senders and forwards outgoing emails for delivery.
virtual server is a program running on a shared server that is configured in such a way that it seems to each user that they have complete control of a server.

virtual server

blade server is a server chassis housing multiple thin, modular electronic circuit boards, known as server blades. Each blade is a server in its own right, often dedicated to a single application.
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 them.

 file server

policy server is a security component of a policy-based network that provides authorization services and facilitates tracking and control of files. 
A database server is responsible for hosting one or more databases. Client applications perform database queries that retrieve data from or write data to the database that is hosted on the server.

database server

A print server provides users with access to one or more network-attached printers — or print devices as some server vendors call them. The print server acts as a queue for the print jobs that users submit. Some print servers can prioritize the jobs in the print queue based on the job type or on who submitted the print job.