Server

What is a server?

A server is a piece of software or hardware whose purpose is to offer a service over a computer network, such as the Internet. Servers can be physical machines, virtual machines, or software that performs server-like functions. The consumers of the service are called clients. The term “client” may refer to a person using the service, or a piece of software (like a Web browser) or hardware (like a phone or computer) the person is using to access the service.

Examples of servers and clients

When you access a website, your browser is acting as a client, and a computer somewhere else in the world is acting as the server. The browser sends a request to the server over the Internet, asking it for the webpage whose URL is in the address bar. The server sends back that page’s content for your browser to display.

Servers and websites aren’t one-to-one. Very busy websites like Google Search are hosted on thousands of servers, all around the world, working together. On the other hand, it’s common for several small, low-traffic websites to all be hosted on a single physical server.

When you use a messaging app on your phone to message a friend, the app is a client, talking to a server operated by the app’s developer. That server is also talking to the app installed on your friend’s phone, and relaying messages back and forth between you.

Server hardware

The term “server” can refer to either hardware or software. Server hardware is a specialized type of computer, designed specifically for responding to requests coming in over a network.

Servers don’t have screens, keyboards, or mice; the only way to interact with them is over a network. Depending on their purpose, they may have very powerful processors, or huge amounts of memory or disk space.

Servers are usually housed in specialized facilities: either a “server room” within a building like an office, or an entire purpose-built, warehouse-like building called a “data center.” These facilities provide electricity, cooling, and network connectivity for servers. They’re also usually kept under tight physical security.

Server software

Server software is the software that waits for requests from clients to arrive over the network, and responds to them as needed. For the most part, it can run on any kind of hardware—you could run Web server software on your laptop if you wanted—but it most often runs on server hardware. When you’re using your computer, phone, or tablet normally, you aren’t running server software.