What is cloud computing? A plain-English guide for business owners

"The cloud" is one of those phrases that everyone uses and few people define. Business owners hear it from software vendors, accountants, IT providers and their own staff, often meaning slightly different things each time. This guide sets out what cloud computing actually is, the forms it takes, what it does well, where it falls short, and what "moving to the cloud" means in practice for a UK business of up to 250 people.

A working definition

Cloud computing is the use of computing resources, meaning servers, storage, databases, software and networking, that are owned and run by a provider in its datacentres and reached over the internet. Instead of buying a server, installing software on it and keeping it in a cupboard in the office, you rent the capability and access it through a browser or an app.

The comparison to electricity is overused but accurate. Very few businesses generate their own power. They connect to the grid, use what they need and pay for it monthly. Cloud computing applies the same model to IT: the provider builds and maintains the infrastructure, you consume the service, and the cost moves from a large capital purchase every few years to a predictable operating expense.

In practice, most small businesses in Hertfordshire and London are already in the cloud without thinking of it that way. Microsoft 365 email, Xero or Sage accounting, a hosted phone system and a web-based CRM are all cloud services.

The three service models: IaaS, PaaS and SaaS

Cloud services come in three broad layers, distinguished by how much the provider manages and how much you do.

For most businesses under 100 people, SaaS is where nearly everything lives. IaaS matters when you have an application that only runs on a Windows server and you want that server out of the building. PaaS is mostly relevant to businesses that develop their own software.

Public, private and hybrid

The second way to classify cloud is by who else shares it.

• Public cloud is the standard model. Microsoft, Amazon and Google run enormous shared datacentres, and your data sits alongside other customers' data, separated by software. It is the cheapest, most flexible and, for the large providers, the best defended option. Microsoft 365 is public cloud.
• Private cloud is infrastructure dedicated to one organisation, either hosted by a provider or built on your own premises. It offers more control at considerably higher cost and complexity, and it makes sense mainly for organisations with contractual or regulatory obligations that rule out shared platforms.
• Hybrid combines cloud services with on-site systems. This is the most common arrangement for established SMEs, and often the right permanent state rather than a halfway house.

Mr Plant Hire, a multi-depot plant and tool hire business headquartered in Enfield that Dig IT has supported for over 15 years, is a good example of hybrid done deliberately. Microsoft 365 and SharePoint handle email, documents and sharing between the group's companies, while Windows servers on site run the core hire systems, protected by both local and cloud backup. Neither half is a compromise. Each workload sits where it works best.

What the cloud does well

The benefits that hold up in practice, rather than in vendor brochures, are these.

Lower and more predictable cost of entry. No server purchase, no server room, no replacement cycle every five years. A per-user monthly subscription is easy to budget and scales with headcount in both directions.

Work from anywhere. Staff sign in from the office, home, a client site or a depot and see the same email, files and applications. Hybrid working is a policy decision rather than an IT project.

Maintenance moves to the provider. Patching, hardware failures, capacity and upgrades happen without your involvement. Your IT provider's time shifts from keeping a server alive to configuring, securing and supporting the people using the service.

Collaboration. Several people editing one document, version history, shared calendars and chat replace email attachments and "final_v3_FINAL.docx".

Resilience of the service. Large providers replicate data across multiple datacentres, so a hardware failure at their end does not take you offline. This is genuine and valuable. It is also where the most common misunderstanding starts, covered below.

Security capability. The big platforms offer multi-factor authentication, Conditional Access, device management and threat detection that a small business could never build alone. The NCSC's cloud security guidance is clear that well-configured cloud services can be more secure than most in-house alternatives.

Access to tools that used to be enterprise-only. Business intelligence, automation, AI assistants, voice and video: all available per user per month with no infrastructure.

The honest limitations

Cloud is not free of trade-offs, and the businesses that regret their move are usually the ones that were not told about these.

• Backup is not included. Providers replicate data so the service stays up. They do not keep an independent copy you can restore from months later. Deleted items are recoverable only within fixed windows, and Microsoft itself recommends backing up your own content. Does Microsoft 365 back up your data covers this in detail.
• Security is shared. The provider secures the datacentre. You secure the accounts, passwords, MFA, permissions and devices. Almost every cloud breach in a small business is an identity failure, not a provider failure.
• It depends on the internet. A single broadband line with no failover is a single point of failure for the entire business. Anything that must keep working during an outage, such as door access or warehouse scanning, should stay local.
• Latency. Applications built for a local network can feel slow when lifted onto a cloud server without redesign. Test with real users before committing.
• Costs can creep. Subscriptions accumulate: unused licences, leavers still licensed, storage add-ons, three tools doing the same job. Without regular review, the monthly bill quietly grows.
• Lock-in. Moving between platforms is possible but never trivial. Choose with the expectation of staying for years.
• Sprawl. Cloud makes it easy to add a new tool without anyone deciding to, which is how businesses end up feeling less organised after moving. Cloud governance for SMEs explains what ongoing structure looks like.

Why the cloud stopped being a big-company technology

Fifteen years ago, cloud meant enterprise contracts, dedicated engineers and complex integration. Three things changed.

First, per-user subscription pricing removed the entry cost. A five-person firm pays the same monthly rate per person as a five-thousand-person one and gets the same platform.

Second, SaaS removed the need for in-house expertise. Microsoft 365, Xero and a hosted phone system can be set up and run by a managed IT provider on the business's behalf. Dig IT's cloud services exist for exactly that reason.

Third, the security tooling caught up. Multi-factor authentication, device management and threat detection are now built into mainstream business plans rather than sold as enterprise add-ons, so a small business can be protected to a standard it could not previously afford.

The result is that cloud adoption among UK SMEs is now the norm rather than the exception. What separates businesses is no longer whether they use the cloud but how well it is configured, secured and governed.

What "moving to the cloud" actually involves

Vendors talk about migration as if it were a single event. In practice it is a sequence of smaller decisions, usually spread over a year or more.

1. Email and documents first. Moving to Microsoft 365 or Google Workspace is the standard first step and delivers most of the visible benefit. The Microsoft 365 migration checklist walks through the phases.
2. Line-of-business applications as they come up for renewal. Accounting, CRM, practice management and job costing systems mostly have cloud versions now. Move them when the contract, the version or the server they run on reaches end of life, not before.
3. Servers last, and not always. An old application that only runs on Windows Server can move to Azure as a virtual machine, be replaced by a SaaS product, or stay on site with proper backup. All three are legitimate outcomes. What to keep off the cloud covers the cases where local still wins.
4. Security and backup at every step. Each service moved needs MFA, sensible permissions, a leaver process and its own backup arrangement.
5. Staff. New logins, new file locations and new ways of working need explaining before the day, not after. Most "the cloud is slower" complaints turn out to be "nobody showed me where the files went".

Dig IT's cloud migration service runs this sequence for businesses across Hertfordshire, west Essex and London, and the article on when to move to the cloud lists the trigger events that make a move worth doing now.

A short glossary

What to do next

If you are unsure how much of your business already runs in the cloud, what is protecting it, or whether the remaining on-site systems should move, a short review of your current setup will give you a clear picture. Dig IT provides this as part of an IT health check, covering cloud services, security configuration and backup in one visit.