What Is Cloud Computing, in Plain Terms

Cloud computing means your software and your files live on a computer in a data centre instead of on your desk. You rent access to that computer, usually by the month, and reach it over the internet.

That is genuinely the whole concept. The marketing around it implies something more ethereal, but there is a building with a specific address holding specific drives, and your photos are on several of them.

What renting changes

The shift from owning a machine to renting capacity changes four things, and they are the reason the model took over.

You stop buying for peak demand. A business that needs forty servers for one week in November used to buy forty servers and leave them idle for eleven months. Renting means paying for forty for a week.

Somebody else handles the hardware. Failed drives, power, cooling, physical security and most patching become the provider’s problem. This is the part organisations value most and it rarely gets mentioned.

Your files are reachable from anything. The same document on your laptop, phone and a borrowed machine, without emailing it to yourself.

A dead device stops being a disaster. The laptop that fell down the stairs held nothing irreplaceable.

Against that: you pay forever instead of once, you need a connection, and your data sits under someone else’s control and someone else’s jurisdiction.

The three layers, briefly

You will see IaaS, PaaS and SaaS used as though everyone knows them. They describe how much the provider manages.

Almost everything an ordinary person touches is SaaS. When you use Google Photos, you are not managing a server; you are using software someone else runs, and the only thing that is yours is the content.

This matters for one reason: in SaaS you cannot fix anything. If the service is down, you wait. That is the trade, and it is usually a good one, because the provider’s uptime is better than yours would be.

Sync is not backup

This is the single most expensive misunderstanding in consumer cloud use.

A synced folder, whether OneDrive, iCloud Drive, Dropbox or Google Drive, mirrors your device to the server and back. It is a copy, in real time, including the copies you did not want:

• Delete a folder by accident and the deletion syncs within seconds.
• Overwrite a document with a bad version and the bad version syncs.
• Encrypt your files with ransomware and the encrypted files sync.

Most services keep deleted items in a trash for 30 days and version history for a similar period, which is a partial safety net rather than a backup. It is enough for the ordinary mistake, and not enough for a mistake you notice in March about something you deleted in January.

A real backup keeps independent copies you can restore from at a point in time. If the only copy of your photos is in a synced folder, you have one copy that happens to exist in two places.

Sync also has a less dramatic cost: those placeholder files still count against your drive, which is why OneDrive quietly fills a C: drive more often than people expect.

Who can read your data

For almost every mainstream service, the provider technically can. Files are encrypted at rest and in transit, but the provider holds the keys, because it needs to decrypt your files to show them to you on a new device, to generate thumbnails and to run search.

That is not a scandal — it is what makes the service convenient. It does mean:

• Staff with sufficient access could in principle read files, and providers control this with internal policy and audit rather than mathematics.
• A lawful request from the relevant jurisdiction can compel disclosure.
• A breach of the provider is a breach of your files.

End-to-end encrypted storage encrypts on your device with a key only you hold. Apple’s Advanced Data Protection for iCloud, and services such as Proton Drive and Tresorit, work this way. The cost is real: lose the key and nothing can recover your data, and server-side features like full-text search stop working.

For most people, mainstream storage plus a password manager plus two-factor authentication is the sensible setting. For documents that would genuinely harm you if exposed, encrypt them before they leave your machine.

Why your bill grows

Cloud pricing is designed around the first gigabyte being free and the hundredth being charged. Three patterns cause surprise:

Photos. Modern phone cameras produce 3–5MB stills and very large videos. The free 5GB on iCloud or 15GB on a Google account fills in a year or two of ordinary use, and the upgrade prompt arrives at the moment your phone stops backing up. What is consuming it is usually less obvious than it looks.

Shared quota. A Google account’s 15GB covers Drive, Gmail and Photos together, so a large mailbox eats photo space and vice versa.

Per-seat software. Office 365 and similar bill per person per month indefinitely. Over five years the total exceeds a one-time licence, which is the point of the model.

Realistic expectations

For an individual, cloud storage is worth it for exactly one reason: your phone will eventually be lost, stolen or broken, and the photos on it are the only genuinely irreplaceable thing you own. Paying a few pounds a month to make that a non-event is a good trade.

Treat the rest with more scepticism. “Cloud” in a product name frequently means nothing more than “we now charge monthly for what used to be a purchase”. Ask what it stores, who can read it, what happens when you stop paying, and whether you could get your data out in a usable format. A provider that answers all four plainly is one worth using.