What Is Cloud Computing? Real Computers Behind the Name

"The cloud" sounds weightless, as if your photos, documents and email drift somewhere above the internet. In reality, the cloud is made of very physical things: rows of computers in large buildings, connected by cables and cooled by industrial equipment. What makes it "the cloud" is not where those machines are but how you use them: over a network, on demand, without owning or running the hardware yourself.

This article explains what cloud computing is, the main types of service, and some common misunderstandings, such as the difference between syncing files and backing them up. It is a general explainer, and it does not compare or endorse any particular provider or price.

Key takeaways

• Cloud computing means using computing resources, such as servers, storage and software, over a network instead of on your own machine.
• Those resources are real computers in data centres. The cloud is not magic, and it is not infinite.
• Providers pool resources and use virtualisation to share them among many customers, who can add or reduce what they use on demand.
• The three common service models are Software as a Service (SaaS), Platform as a Service (PaaS) and Infrastructure as a Service (IaaS).
• Syncing is not the same as backing up. If you delete a file in a synced folder, the deletion usually syncs too.
• Security, privacy and availability depend on both the provider and the customer, and the split of responsibilities varies.

The cloud is real computers somewhere else

When you save a photo to an online service, the file is stored on servers owned by the company that runs the service, or by another company it rents space from. Those servers sit in data centres: buildings filled with computers, storage devices, networking equipment, backup power and cooling. Your device talks to them over the internet.

Using the cloud, then, simply means that the computer doing the work, or holding your data, is not the one in front of you. You might not know exactly which machine in which building is handling your request, and in most cases you do not need to.

What "on demand" and "pooled" mean

Cloud services are usually described with a few key ideas:

• On demand: you can start using a resource when you need it and stop when you do not, often without talking to a person.
• Pooled resources: a provider's hardware is shared among many customers. The provider assigns capacity as needed.
• Scalable: customers can increase or decrease how much they use, within limits.
• Measured: usage is tracked, and in many services customers pay for what they use.

A technology called virtualisation makes much of this possible. It allows one physical computer to be divided into several separate virtual machines, each behaving like its own computer. That lets a provider use hardware efficiently and hand out slices of capacity to different customers.

It is worth being clear that "on demand" does not mean unlimited. Cloud capacity is large but finite, and providers manage it with limits, quotas and prices.

The three main service models

Cloud services are often grouped by how much the provider manages for you.

Software as a Service (SaaS)

You use a finished application through a browser or app, and the provider runs everything behind it. Web-based email, online document editors and video-calling tools are typical examples. You manage your own content and settings, but not the underlying software or servers.

Platform as a Service (PaaS)

The provider supplies a ready-made environment for building and running applications. A developer can write code and deploy it without managing the operating system or servers. A hypothetical example is a service where a team uploads a web application and the platform takes care of running it.

Infrastructure as a Service (IaaS)

The provider offers basic building blocks such as virtual machines, storage and networking. The customer decides what software to install and manages more of the setup. A company might rent virtual servers instead of buying its own.

The further you move from SaaS toward IaaS, the more control and responsibility you have.

Public, private and hybrid clouds

Clouds can also be described by who can use them:

• A public cloud is run by a provider and shared among many customers.
• A private cloud is used by a single organisation, either on its own premises or hosted for it.
• A hybrid approach combines the two, keeping some systems local and using the public cloud for others.

Many organisations and individuals use a mixture of local and remote storage and services without calling it by any of these names.

Syncing is not backing up

One of the most common misunderstandings involves cloud storage for personal files. Syncing keeps the same files up to date across your devices. If you change a file on your laptop, the change appears on your phone. But that also means a mistake, such as deleting a folder, can spread to every device.

A backup is a separate copy that is kept so you can recover files after something goes wrong. Many services offer version history or a recycle bin that holds deleted files for a limited time, which can help. Still, it is worth understanding what your particular service does and does not keep, and for important files, a separate backup is a sensible habit.

Security, privacy and who is responsible

Moving data to the cloud does not remove the need to look after it. Responsibility is usually shared:

• The provider is responsible for securing the data centres, the hardware and the core services.
• The customer is responsible for matters such as choosing strong passwords, turning on extra sign-in protection, deciding who can access files and not sharing links carelessly.

The exact split varies by service type and provider, which is why it is worth reading how a service describes its responsibilities. Questions about privacy also depend on a provider's policies and on the laws that apply. Access permissions deserve regular checks: shared folders and public links can stay open long after they are needed.

Availability matters, too. Cloud services can have outages, and your access depends on your internet connection. For anything critical, think about what you would do if the service were unavailable for a while.

Advantages and trade-offs

Cloud computing can offer real benefits:

• Access to your files and apps from different devices.
• Less need to buy and maintain your own hardware.
• The ability to scale up or down as needs change.

It also has trade-offs:

• Dependence on an internet connection and on the provider's reliability.
• Questions about where data is stored and who can access it.
• Costs that can grow with usage, which are worth monitoring.

None of these is a reason to avoid the cloud, only to use it with open eyes.

Frequently asked questions

Where is "the cloud" physically?

In data centres, which are buildings full of servers and storage equipment connected by networks. They are run by cloud providers around the world.

Is the cloud the same as the internet?

No. The internet is the network that connects devices. The cloud refers to computing resources and services that you reach through that network.

Is cloud storage a backup?

Not by itself. Cloud storage often syncs changes, including deletions. A backup is a separate copy kept for recovery, though some services offer version history that can help.

What is the difference between SaaS, PaaS and IaaS?

SaaS delivers finished software. PaaS provides an environment for building and running applications. IaaS provides basic computing resources such as virtual servers and storage.

Is data in the cloud safe?

It depends on the provider's security and on how the customer configures access. Responsibility is shared, so both sides matter.

Sources and further reading

• What is the cloud? (Cloudflare Learning Center)
• Cloudflare and the cloud (Cloudflare Learning Center)

Related reading on FactNest: How the internet actually works and How batteries work.