What is 'the cloud', really? Someone else's computer, rented by the minute

"The cloud" isn't fluffy and it isn't far away. Point at it: it's someone else's computer, in a building, that you rent by the minute.

The cloud is renting computing over the internet instead of owning the machines yourself.

There's a standard definition. NIST (the US standards body): "Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources … that can be rapidly provisioned and released with minimal management effort."

Two of its five characteristics are the whole appeal, in plain words. "On-demand self-service": you can spin up a server yourself, instantly, without phoning anyone. "Broad network access": you reach it over the internet from any device.

So a server "in the cloud" is a slice of a real machine in a data centre you'll never visit. You rent it by the second, and hand it back when traffic drops.

Your app already lives there, and so does ours: this very site runs on cloud computers (Cloudflare's) we'll never physically see. That's also why your data sits on someone else's hardware, which is why backups are your responsibility, not theirs.

Try it with the rules off. In the sandbox, imagine turning your app off for a month. In the cloud the bill drops toward zero; with your own bought server, you still paid for the hardware. That difference is the model.

Next in making it real: What is an edge / CDN?.