Cloud computing
Cloud computing is the delivery of computing resources — servers, storage, databases, networking and software — over the internet on demand. Instead of buying and maintaining physical machines, organisations rent capacity from a provider and pay for what they use. The "cloud" is simply someone else's data centre, made accessible through the network.
The idea reshaped how software is built and sold. A startup can now launch a global service without owning a single server, and an established company can scale up for a busy shopping season and scale down afterwards without wasting money.
How it works
Providers run vast farms of servers grouped into regions and availability zones spread across the world. Virtualisation software lets many customers share the same physical hardware while staying isolated from one another. When you request resources, automation places your workload on a machine with spare capacity and wires up storage and networking around it.
From the user's point of view the result feels elastic: capacity appears within minutes, and it disappears just as easily. Behind the scenes, orchestration systems watch usage, move workloads to balance the load, and replace failed machines so that services keep running.
The three service models
Infrastructure as a service (IaaS) provides raw virtual machines, storage and networks. The customer installs and manages the operating system and everything above it. Platform as a service (PaaS) adds a managed environment for running code, so developers focus on the application rather than the servers. Software as a service (SaaS) delivers a finished application, such as webmail or a document editor, that people simply log into.
The trade-off between the models is control versus convenience. The lower you go, the more you can customise and the more you must maintain yourself.
Deployment models
A public cloud is open to many customers and is the most common arrangement. A private cloud serves a single organisation, often for regulatory or security reasons, and may sit in the company's own building. Hybrid setups mix the two, keeping sensitive data close while using public capacity for flexible work. Many firms now spread workloads across several providers to avoid depending on one.
Why organisations move to it
The main attractions are cost and flexibility. Capital spending on hardware becomes a predictable operating expense, and teams can experiment cheaply. Providers also handle maintenance, backups and security patching for the underlying layer, letting small teams operate at a scale that once required large IT departments. Global reach comes almost for free, because a service deployed in one region can be replicated to others.
Risks and criticisms
Concentration is the central concern. When much of the internet runs on a handful of providers, an outage or a pricing change can affect millions of users at once. Customers also worry about data privacy and about which laws apply when data crosses borders. Moving between providers can be difficult because each offers slightly different tools, a problem often called vendor lock-in. Costs can creep up too, since pay-as-you-go billing rewards careful monitoring.
Cloud as a platform, not just storage
The cloud has grown from a way to rent servers into a platform for building almost any digital service. Providers now offer managed databases, messaging systems, machine-learning tools and ready-made components that developers assemble like building blocks. This lets small teams create products that once required large engineering departments, and it has made rapid experimentation and continuous updates normal.
The model also changes how software is delivered. Applications are increasingly split into small services that scale independently, and they are updated many times a day without users noticing. This flexibility is powerful but adds complexity: teams must manage configuration, monitor many moving parts and control costs. The cloud has therefore shifted the main challenge of running software from owning hardware to operating systems well, and it has made skills in automation and security more valuable than ever.
What the cloud means for everyday users
Most people use cloud computing without thinking about it. Webmail, online documents, photo libraries, streaming services, video calls and mobile backups all live in someone else's data centre and reach the user over the internet. This is why work started on one device can be finished on another, and why a lost phone does not always mean lost data.
Convenience comes with dependence. When services run remotely, users rely on the provider staying online, on a working connection and on terms they did not negotiate. Outages can halt work, price changes can surprise customers, and account decisions can affect access to years of personal content. For individuals, the practical lesson is to choose services thoughtfully, keep local copies of what matters, and understand where their data actually sits.
Key points
- Cloud computing rents computing resources over the internet instead of owning hardware.
- Virtualisation and automation let many customers safely share the same physical servers.
- The three service models are IaaS (infrastructure), PaaS (platform) and SaaS (software).
- Deployments range from public and private to hybrid and multi-cloud.
- Benefits include elasticity, lower upfront cost and global reach.
- Main risks are provider concentration, data privacy, lock-in and runaway costs.