Server

Say you're reading a webcomic late at night or listening to music at dawn on your phone. Where is all that data actually stored? Your phone doesn't hold thousands of webcomic episodes. The data sits on another computer, far away on the internet.

When you tap a link, it's like sending that computer an order slip: "Show me episode 1 of this webcomic!" The computer finds the stored image files and sends them to your phone right away. A computer that takes requests from a customer (the client) and serves up what they asked for is called a 'server.'

A server for a popular website or app never knows when the next customer will show up. So it usually stays plugged in and connected to the internet 24 hours a day, 365 days a year. If that computer shuts off or breaks, you lose access, and people say, "The server crashed!"

A server isn't made of magical, brand-new parts. It has a CPU, memory, and storage, just like the desktop you use at home. In principle, your own laptop could be a great server if you installed server software and left it on all day.

But a company's server has to keep going even when thousands or tens of thousands of users arrive at once. So it packs in much more powerful processing parts. It may also double up on parts in case something fails, such as having two power supplies.

A place where an entire building is set aside to keep huge numbers of servers safe and cool is called a 'data center.' It has backup power for blackouts (UPS units and generators) and big cooling systems to get rid of heat. Dust and temperature are tightly controlled so we can get online whenever we want.

To be a bit more precise, 'server' doesn't only mean a particular box of hardware. It can also mean the 'role of a program' running inside a computer.

For example, say you create a multiplayer game room on your computer to play with friends. At that moment, your computer is acting as a server that manages the game data. But when you use the same computer to search the web, you're the customer asking another site's server for information. In other words, you're a 'client.'

In the end, what makes a server a server isn't how the hardware looks. It's 'the software role of receiving requests and providing the right data.' Servers get different names depending on their job: a web server hands out web pages, a mail server delivers email, and a game server calculates positions in a game.