What is a server?
A server is a PC that is running software that is responsible for coordinating some form of communication between nodes on a network. Servers provide shared resources on a network such as file storage, databases, email, and web services. There are four requirements for a server: computer hardware, operating system (OS), server software, and connections between the devices on the network. The hardware can be as simple as the hardware on a standard desktop PC, or as complex as those found in a server farm. The minimum requirements for the OS and the server software are that they are robust enough to support networking activities. A connection to the devices that will use the services provided by the server can be wired or wireless.
There are many types of servers:
Web servers. Web servers are one the most abundant servers in the market today. A web server is an application server that hosts programs and data requested by users across the internet or intranet. A web server responds to requests from browsers running on client computers for web pages, or other web-based services.
Mail servers. A mail server is a very common type of application server that receives emails sent to a user and stores them until requested by a client on behalf of the user. Having an email server allows for a single machine to be properly configured and attached to the network at all times, ready to send and receive messages, rather than requiring each machine on the network to have their own email subsystem running continuously.
Database servers. Databases store the copious amount of data used by companies and users. A database server is a program that listens for requests to retrieve or store data in a particular database. Databases need to be accessible to multiple clients simultaneously. Common database server applications include Microsoft SQL Server, DB2, Oracle, and Informix.
Proxy servers. A proxy server acts as an intermediary between a client and a server. A proxy server is primarily used as a security measure as it takes requests from clients and passes them along to another server, without either entity needing to be directly connected to one another.
Monitoring servers. Monitoring servers listen to the network and receive every client request and server response in order to watch over the health of the network.
DNS servers. Domain Name System (DNS) servers are application servers that provide name resolution to client computers by converting names easily understood by humans into IP addresses that are machine-readable. When a client needs the address of a systems it will send a DNS request with the name of the desired resource to a DNS server, which then responds with the necessary IP address from its table of names.
File servers. File servers store and distribute files. Files can be stored on a server to be shared with multiple clients or users.
Print servers. Print servers allow numerous clients to submit printing requests, eliminating the need for each workstation to have its own printer.