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What is a server and how does it work?

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A server provides other devices or applications with services, data, and computing power. It can operate on a home network, within a company network, or on the internet. It’s important to distinguish between the server software (the programs and services it runs) and the physical server (the hardware). Both meanings are correct and widely used.

Below you’ll find a clear explanation of how servers work, the main server types, security best practices, architecture, and real-world examples.

09.10.2025 | Reading time: 6 minutes

How a server works

A server waits for requests and returns a response. A client, such as your browser or an app, opens a connection and sends a request. The server validates it, runs business logic, accesses the data, and sends back a response.

This process relies on protocols like HTTP, SMTP, IMAP, DNS, and FTP, and uses ports for addressing.
Modern servers work in parallel and asynchronously, use caching to speed up responses, and load balancing to distribute traffic across multiple instances.

Server software vs. physical server

The server software is the set of programs and services that deliver functionality. Examples include:

  • Web server for websites and apps
  • Mail server for e-mail
  • Database server for structured data


These services run continuously, serve many clients, and keep logs of events.

The physical server is the hardware machine that hosts these services. It’s designed for 24/7 operation, reliability, and high performance.
It’s often referred to as a host. A single host can run several services at the same time.

The client-server model explained

The client-server model is the foundation of most online services. Clients send requests, and servers send back responses.

For example, your browser requests a page, the web server prepares the content, and sends HTML, CSS, and scripts.
This same pattern powers streaming, online banking, gaming, and cloud storage.
Separating client and server ensures scalability, security, and easy maintenance.

Host vs. server — what’s the difference?

A host provides resources such as CPU, RAM, storage, and network connectivity. The server software runs on top of it.

A simple rule: host = device, server = service. In everyday language the two terms are sometimes mixed up, so context matters.

Types of servers and when to use them

Server type

What it does

When to use it

Web server

Delivers websites and APIs

Hosting sites, web apps, headless CMS

Mail server

Handles email sending and storage

Company email, newsletters

Database server

Stores and serves structured data

Online stores, ERP, CRM, analytics

File server

Centralises file storage and sharing

Team folders, backups, sync

DNS server

Translates domain names into IP addresses

Internet name resolution

Application server

Runs core business logic

ERP systems, CRM, back-end apps

Proxy or cache

Speeds up responses, filters requests

Improve security, optimise performance

Streaming server

Streams audio and video

Music, TV, webinars, live events

Directory service

Manages user identities and access rights

Single Sign-On, role management

What makes up a server

A server typically includes:

  • Processors for computation.
  • RAM for fast data access.
  • Storage for persistence.
  • Network interfaces for connectivity.
  • Redundant power supply for reliability.


In data centers, rack-mounted chassis allow for high density. You’ll often find RAID for fault tolerance, ECC RAM for error correction, and remote management to control servers without direct physical access.

Physical, virtual, and cloud servers compared

Type

What it is

Why choose it

Best for

Physical server

A dedicated piece of hardware with one OS

Maximum control, best performance

Databases, specialised workloads

Virtual server

Multiple virtual machines on one host

Flexible, isolated, efficient use of hardware

Web stacks, app environments, testing

Cloud server

Virtual instances from a cloud provider

Quick to deploy, scalable, pay as you go

Projects with variable load, global reach

Inside a data center

A data center houses many servers, storage arrays, and network devices mounted in racks.
It provides redundant power, UPS systems, backup generators, cooling, fire protection, access control, and continuous monitoring.

Networks are segmented, services are monitored and backed up, and operations follow planned maintenance procedures.
The goal is high availability and stable performance.

How to keep your server secure and reliable?

  • Least privilege
    Grant only the rights strictly necessary to authorised people and systems. Separate and audit admin access.
  • Updates and patches
    Keep the OS and services up to date to fix known vulnerabilities.
  • Encryption
    Use TLS to protect data in transit and encrypt sensitive data at rest.
  • Backups and recovery
    Run regular backups, test restore procedures, and define clear RTO and RPO targets.
  • Logging and monitoring
    Centralise logs, analyse them, and set alerts to catch attacks, errors, and bottlenecks early.
  • Network segmentation
    Separate production, testing, admin, and public services. Allow only required connections.
  • Strong authentication
    Use strong passwords, multi-factor authentication, and secure key management. Never store credentials in code or public repositories.

Everyday examples

  • Web browsing
    Your browser sends an HTTP/HTTPS request to a web server, which fetches content from a database and sends it back.
  • Email
    The client sends messages to an SMTP server, and the recipient reads them via IMAP. Antispam, antivirus, and encryption work server-side.
  • Streaming
    A streaming server segments media, and a CDN distributes it globally. Your player buffers and plays the stream.
  • Online shop
    The web server shows the catalogue, the application server validates the cart, the database server stores the order, and the payment provider processes it.

Scaling from a single server to a modern architecture

Start with a virtual server hosting web, app, and database.
As traffic grows, separate the roles, scale web and app horizontally, replicate and cache the database, and serve static files via a CDN.
Add queues for background jobs, observability (metrics, logs, traces), and Infrastructure as Code for reproducible environments.

Key takeaways

A server can mean a service that responds to requests or the hardware that runs it.
In the client-server model, clients request and receive responses.

Key roles include web, mail, database, file, DNS, application, proxy, and streaming servers.
Servers can be physical, virtual, or cloud-based. With good security, backups, monitoring, segmentation, and scaling, your infrastructure stays reliable and high performing.

FAQs


Can any computer become a server?

Yes. With the right software, any computer can deliver services. What differs is reliability, security, and performance.

Is a host the same as a server?

Not exactly. The host is the environment with resources, the server is the service running on them. The words are often used interchangeably.

Do I need multiple servers?

Yes, if you care about security, stability, and scalability. Splitting roles limits the impact of failures and lets you optimise resources.

What is the advantage of cloud servers?

Fast start-up, elastic scaling, pay-as-you-go pricing, and global availability. But you must control costs, security, and architecture carefully.

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