What is cloud computing? IaaS, PaaS and SaaS explained
In short: Cloud computing means renting computing power, storage and software over the internet instead of owning the hardware. IaaS, PaaS and SaaS differ in how much the provider manages for you.
The simple idea
"The cloud" is someone else's data centre that you use over the internet. Instead of buying servers, you rent what you need, scale up or down in minutes, and pay for what you use.
The three service models
| Model | You get | You manage | Everyday comparison |
|---|---|---|---|
| IaaS (Infrastructure) | Virtual servers, storage and networks | Operating system, apps, data, security settings | Renting an empty flat |
| PaaS (Platform) | A ready platform to run your code or database | Your app, data and access | A furnished flat |
| SaaS (Software) | Finished software you just use, like webmail or online office apps | Your data, users and settings | A hotel room |
Deployment types
- Public cloud: shared provider infrastructure available to anyone.
- Private cloud: cloud-style infrastructure dedicated to one organisation.
- Hybrid cloud: a mix of on-premises systems and public cloud, connected together.
Benefits and watch-outs
| Benefits | Watch-outs |
|---|---|
| No hardware to buy or maintain | Costs can grow quickly without monitoring |
| Scale up or down in minutes | Misconfiguration is the top cause of cloud breaches |
| Global reach and built-in redundancy | You depend on your internet connection and the provider |
Next step: who secures what in the cloud.
Real-world example: a small office leaves its server cupboard
A ten-person estate agency used to keep an old server in a cupboard for email and shared files. When it failed, nobody could work until a technician arrived, and backups depended on someone remembering to swap a USB drive.
The agency moves to an online office suite for email, documents and file sharing. That is SaaS: they just use the software. Their property-listing database moves to a managed cloud database, which is closer to PaaS. Staff can now work from viewings on their phones, and the provider looks after the hardware and keeps the service running.
The agency still has jobs to do: managing user accounts, turning on MFA, removing leavers promptly and checking who files are shared with. Moving to the cloud changes the work; it does not remove it.
Try this: list the cloud services you already use, such as webmail, photo backup, music streaming or online documents. For each one, decide whether it is SaaS, and think about what you still control: your password, your MFA and your sharing settings.
Key takeaways
- Cloud = renting computing over the internet.
- IaaS, PaaS, SaaS: the provider manages more as you move up.
- Public, private and hybrid are the main deployment types.
- Watch costs and configuration from day one.
Original content written by Mohamed Fayas for FM TecHub. © 2026 FM TecHub. You're welcome to share a link to this page; please don't copy the text elsewhere without permission.