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Beginner

What is a server

Also known as: web server, cloud server, server computer

Definition

A server is a computer, or a program on one, that receives requests from other programs, such as a visitor's browser, processes them and sends back an answer.

Why it matters

When your site or app goes live, someone's server runs it, usually your hosting company's, and every visit, order and form depends on that server answering.

Common mistakes

Reading 99% uptime as almost perfect, when it allows more than three and a half days of downtime a year.

Related terms

Worked exampleIllustration

What an uptime promise means in hours

An owner compares hosting plans that promise 99%, 99.9% and 99.99% uptime.

  1. A year has 365 days of 24 hours.

    8,760 h

  2. At 99% uptime, 1% of the year may be down.

    87.6 h

  3. At 99.9%, 0.1% of the year may be down, about 44 minutes a month.

    8.76 h

  4. At 99.99%, 0.01% of the year may be down.

    ≈ 53 min

  5. The owner asks each host which figure is in the contract and what it pays back when it misses it.

Each extra 9 cuts the allowed downtime tenfold, and a service credit returns part of the fee, not the lost sales.

Illustration

How it works

Client, Request, Server, ResponseClientbrowser orappServerstores andprocessesRequestResponse

The server answers. It waits for requests, does the work and sends back only what the client should see.

The server is the computer that answers: it receives every request, processes it, and returns the data.

Where your server can live

Where it livesWho fixes it at 3 am

The arrow points to more control and more work for you.

A computer in your own room. The power, the cooling, the spare parts and the 3 am call are all yours.

Down the ladder you get more control and more work. The managed rung is where the provider takes the work back.

Definition

A server is a program that waits for requests from clients and answers them, and by extension the computer that runs it. The HTTP standard puts it this way: an HTTP server is a program that accepts connections in order to service HTTP requests by sending HTTP responses. So a web server (the program) runs on a server (the machine). The types an owner meets are web servers, email servers, database servers, application servers that run a site's business logic, and a file server or NAS (a network storage box) in the office. The same machine can be a server and a client at once: a web server that asks a payment provider to approve a charge is that provider's client. Serverless services still run on servers, the provider only hides and manages them.

Why it matters

The figure owners meet when they buy hosting or a server is uptime, the share of time it is available, and each extra 9 matters more than it looks. A service level agreement (SLA) says what you get when the promise is missed, and it pays back part of the fee, not your lost sales. AWS, for example, commits to 99.99% monthly uptime for EC2 run across two or more availability zones, and credits 10% of the fee below that, 30% below 99.0% and 100% below 95.0%. Where the data centre sits matters for speed and sometimes for contracts.

Directly related: Client (computing), Hosting, Cloud.

Improvement tips

  • Ask your host which uptime figure is in the contract and what it pays back when it is missed.
  • Monitor the site from outside, so you hear about downtime before your customers do.
  • Keep the server's operating system and software updated, or choose managed hosting so someone else does it.
  • Keep backups off the server itself, so one failure cannot take both.

Common mistakes

  • Running the site, the database and the only backup on one server.
  • Leaving default passwords and open ports on a new server.
  • Forgetting that a sale or a campaign will bring more traffic than the server usually handles.
Client vs Server

Related terms

TechnologyBeginner

Client (computing)

A client, in computing, is the program, such as a browser or an app, that sends a request to a server and shows you the answer. It is not your paying customer.

TechnologyBeginner

Hosting

Hosting is a service that rents you space on a server connected to the internet all the time, so your website is available to every visitor.

TechnologyBeginner

Cloud

The cloud, or cloud computing, is renting a provider's servers, storage and software over the internet instead of running your own, paid monthly or by use.

TechnologyIntermediate

Back-end

Back-end is the part of a website or app that users never see: it saves orders, checks stock, charges cards and keeps accounts, running on a server.

TechnologyBeginner

Database

A database is an organised collection of information, usually tables of rows and columns, that software can search, update and link, like customers to orders.

TechnologyIntermediate

Authentication

Authentication is the check that a user is who they claim to be, using something they know, something they have or something they are.

Quick check

What is the main job of a server?

Choose an answer

Frequently asked questions

Do I need to understand servers before I start my business?
Only the idea: a server is the always on computer that answers when someone opens your site or app. For most small businesses the server belongs to the hosting company or to a SaaS vendor, and your job is to choose them well.
When does a server first become relevant for a new business?
The moment your site or app goes live, someone's server runs it, usually your host's. Business email usually runs on a hosted service too, so you rarely need a server of your own at the start.
Do I need to buy a server for my startup?
Almost never at the start. You rent server capacity through hosting or a cloud provider and pay monthly, and the provider owns and maintains the hardware. Buying hardware makes sense only for special needs, such as equipment that must stay in the office.
Should I manage my own server or use managed hosting?
Managed hosting suits most small businesses, because the provider handles updates, security patches and backups. Your own server gives more control but needs someone who knows how to update and secure it, every month.
Why does server performance matter for a business already running?
A slow server makes every page slow, and an unavailable one closes the shop. The effect is largest in your busiest hours, when a sale or a campaign brings more visitors than usual.
What goes wrong when a business ignores server security?
Unpatched software and default passwords let attackers in to steal data, plant malware or use the server to attack others. The fix is routine work: updates, strong unique passwords, closed ports and working backups.
Can I upgrade my server without stopping the business?
Usually with a short break. In the cloud you can move to a larger server within minutes, usually with a restart, and without a fixed address the server may get a new public IP. Plan the change for a quiet hour and test it on a copy first.
How do I know my server is struggling?
Pages slow down at busy times, visitors see timeout errors, or monitoring shows CPU and memory near their limits. Upgrade before a big sale, not during it.
What does server actually mean in plain words?
A computer that never sleeps and answers requests. When someone types your address, a server receives the request and sends back the page.
Is running a server in my office risky?
For most small businesses, yes: power cuts, internet outages, theft and missed updates all land on you. A data centre is safer for most small businesses, although an office file server can still make sense for large local files.
Do I need a server engineer to keep my site online?
Not with managed hosting or a website builder, where the provider runs the servers. You need a developer or an administrator when you run your own software on your own or rented servers.
What is the difference between a cloud server and a physical server?
A physical server is one machine in a room. A cloud server is a virtual machine that the provider runs on its large pool of physical hardware, so you can resize or replace it without touching any hardware.

Sources: IETF RFC 9110, HTTP Semantics, 2022, section 3.3, Amazon Web Services, Amazon Compute Service Level Agreement, last updated 25 May 2022 (aws.amazon.com/compute/sla), read 23 September 2026, Amazon EC2 User Guide, Change the instance type (docs.aws.amazon.com), read 23 September 2026

Last reviewed: 2026-09-23

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Anna, Beautician

Anna

Beautician

After I finished a cosmetology course at a leading company, I was confused. I didn't know how to open a business, what to sell from home, or how to bring in clients. Since I reached out to Mobius, everything has changed. We built an organized plan with clear steps and no unnecessary risks. Today I see results, and I'm growing and developing every month.

Mark, Massage therapist, Gan Yavne

Mark

Massage therapist, Gan Yavne

When I finished a massage course, I imagined a different world. I found out it's a hard field, and financial stability isn't easy to find. When I came to Mobius, something changed. We started an organized process and built a business plan. Without Mobius? I probably would have given up. Today I believe in myself and in my own path.

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