A server is a computer, or a program on a computer, whose job is to answer requests from other devices. Your phone asks for a web page, an email or a photo, and a server somewhere sends it back. The word describes a role, not a special kind of box: a laptop can act as a server, and one large machine can run dozens of them.
The client and server pattern
Almost everything online follows one model. A client, such as a browser or app, sends a request across the network to a known address and port. The server program listening there processes it and sends a response. A web server answers HTTP requests for pages, a mail server accepts and delivers email, a database server answers queries, and a DNS server translates names into addresses. The client never needs to know how the server stores anything; it only needs the agreed protocol.
Hardware, virtual machines and the cloud
Physical servers in data centres are built for running nonstop: redundant power supplies, error-correcting memory, and remote management. Most of today's servers are virtual, many running on one physical machine, as with a VPS. "Serverless" platforms still use servers; the provider just starts and stops them for you per request, so you never manage one directly.
The servers behind one florist order
When a customer opens a florist's online shop, several servers take part in a second or two. A DNS server returns the shop's address. The web server sends the page. An application server checks stock in a database server. A payment provider's servers handle the card. If any of those is slow or down, the customer sees the delay or error, even though they think they are using just "the website".
What a small business needs to know
Most owners never touch a server. Hosting companies and website platforms run them for you. It helps to understand the word for two reasons: error messages like "500 Internal Server Error" mean something broke on the server side rather than in the visitor's browser, and choosing a host is really choosing who runs your servers and how well.
Misunderstandings that cause trouble
- Running a business site from an office PC. Home and office connections, power cuts and sleep settings make this unreliable.
- Confusing the server with the domain. The domain is a name; the server is the machine the name points to. You can move one without the other.
- Thinking more servers always means faster. Extra machines help only if traffic is split across them, which is what a load balancer does.
Related terms
- Web server: the server role that delivers websites.
- Localhost: a server running on your own computer.
- Port: how one machine runs many server programs.
- VPS: a virtual server you rent.