Cloud Computing definition
Cloud computing is the on-demand delivery of computing resources, such as servers, storage, databases, networking and software, over the internet with pay-as-you-go pricing. Instead of buying and running their own data centers, organizations rent capacity from providers like Amazon Web Services, Microsoft Azure and Google Cloud and scale it up or down as needed.
How does cloud computing work?
Cloud providers operate large data centers grouped into regions around the world, each split into isolated availability zones. Virtualization divides physical servers into many virtual machines, and software-defined networking and storage do the same for networks and disks. Customers request resources through a web console, an API or infrastructure-as-code tools, and receive them in minutes rather than the weeks a hardware purchase takes. Usage is metered and billed by the second, hour or request.
The US standards body NIST describes five essential characteristics: on-demand self-service, broad network access, resource pooling across many customers, rapid elasticity and measured service. Those traits, more than any specific technology, separate cloud computing from traditional hosting or a rented server in someone else's data center.
Cloud service models
Each service model hands more responsibility to the provider. The further up the stack you go, the less you manage and the less you can customize. Most organizations use all of them at the same time, choosing the model per workload.
- Infrastructure as a Service (IaaS): virtual machines, storage and networks, such as Amazon EC2.
- Platform as a Service (PaaS): managed runtimes for deploying code, such as Azure App Service.
- Software as a Service (SaaS): complete applications used through a browser, such as Microsoft 365.
- Serverless and functions: code that runs per event with no servers to manage, such as AWS Lambda.
Public, private, hybrid and multi-cloud
Public cloud resources are shared infrastructure run by a provider and rented by many customers. A private cloud is dedicated to one organization, either in its own data center or hosted. Hybrid cloud connects private infrastructure with public cloud so workloads and data can move between them, and multi-cloud uses services from more than one public provider. Most large organizations end up with some mix, driven by regulation, legacy systems and cost.
Benefits and drawbacks
The cloud removes large upfront hardware spending, lets capacity follow demand, puts global infrastructure within reach of small teams and offers managed databases, AI services and analytics that would be expensive to run in-house. Built-in redundancy across zones makes resilient architectures far easier to build than in a single data center.
The drawbacks are real too. Bills can grow quickly without cost governance, data transfer out of the cloud carries fees, and proprietary services create lock-in. Security follows a shared responsibility model: the provider secures the infrastructure, but customers remain responsible for configuration, identity and data, and misconfiguration is a leading cause of cloud breaches.
Example and how to get started
A retailer that sees traffic spike tenfold during festive sales runs its storefront on auto-scaling cloud servers behind a CDN. Capacity grows for the sale and shrinks afterward, so the company pays for peak capacity only while it needs it. Moving to the cloud usually follows one of several strategies, from rehosting servers unchanged to refactoring applications into cloud-native services. Nexzem plans cloud migrations workload by workload, with cost estimates and security baselines agreed before anything moves.