When talking in the technical sense, a server is considered an instance of a computer program which accepts and responds to requests made by another program, also known as a client.
Less formally, any that device runs a server software can also be considered a server as well. Servers are for managing network resources. For example, a user might want to setup a server to control access to a network, send/receive an e-mail, manage print jobs, or even host a website.
Certain servers are committed to a particular task, sometimes referred to as dedicated servers. As a result, you will have a number of dedicated server categories such as print servers, file servers, network servers, and database servers. Though, a lot of servers today are shared servers, they could just take on the responsibility of e-mail, DNS, FTP, and also various websites in the case of a web server.
Since servers are quite commonly used for delivering services that are needed constantly, they are usually never turned off. Therefore, when servers fail, they can cause the network users and company a lot of problems. To avoid these issues, servers are commonly high-end computers setup to be fault tolerant.
Common Types of Servers
There are some dedicated servers where the server operates with only one function; certain implementations will use one server for several purposes.
A large, general-purpose network supporting a medium-sized company will most probably deploy a few different types of servers.
Web servers show pages and run applications using a web browser.
The server your browser is connected to currently is a web server capable of delivering this page; really, any image you may see. In this case, the client program is most probably a browser such as Firefox, Chrome, Opera, Safari, or Internet Explorer.
A web server is used for many things, in addition to sending simple text and images, it is capable of uploading and backing up files online using a cloud storage service or online backup service.
Email servers ease the process of sending and receiving email messages.
Once you have an email client on your computer, the software will be connected to an IMAP or POP email server so it is able to download messages to your computer then to an SMTP server to send messages back using the email server.
An FTP server allows the moving of files using File Transfer Protocol tools.
You can access an FTP server remotely using an FTP client program such as the popular FileZilla Client.
What Identity servers do is allow logins and security roles for authorized users.
Many different types of specialized server types allow computer networks. This is separate from the common corporate types, home users generally interfacing with game servers, chat servers, audio streaming services, or others.
Network Server Types
A lot of networks on the internet operate using a client-server networking model combining websites and communication services.
Another model is called peer-to-peer networking, which allows all devices on a network to work as either a server or a client on an as-required basis.
Peer networks give a greater degree of privacy since communication between computers is much more targeted, although many implementations of peer-to-peer networking are not quite robust enough to allow for big traffic spikes.
A cluster is generally used in computer networking when a person wants to refer to implementations of shared computing resources. Usually a cluster combines the resources of two or more computing devices which are capable of otherwise functioning separately for some common purpose; they are usually a workstation or a server device.
A web server farm is a number of networked web servers, each one with access to content on the same site that functions as a cluster, theoretically.
Though, purists debate the technical classification of a server farm as a cluster, while being dependent on the details of the hardware and software configuration.
Servers at Home
Since servers are simply software, people can run servers from home, accessible only to devices attached to their home network. For example: certain network-aware hard drives use the Network attached storage server protocol to permit several PCs on the home network to access a shared set of files.