On-demand computing, IaaS, PaaS, SaaS, public cloud, private cloud, hybrid cloud, scalability, regions, and shared responsibility
Cloud computing
Cloud computing is a model for using shared computing resources over a network on demand, letting people and organizations rent servers, storage, databases, software, networking, and platforms without owning all the underlying infrastructure.
What cloud computing is
Cloud computing lets users access computing resources such as servers, storage, databases, networking, software, and development platforms over a network. Instead of buying and operating every machine directly, organizations can rent capacity from cloud providers and adjust usage as needs change.
NIST definition
The NIST definition describes cloud computing as convenient, on-demand network access to a shared pool of configurable computing resources that can be rapidly provisioned and released with minimal management effort. Its essential characteristics include on-demand self-service, broad network access, resource pooling, rapid elasticity, and measured service.
Service models
Infrastructure as a Service provides virtual machines, storage, and networking building blocks. Platform as a Service gives developers managed environments for deploying code without handling as much infrastructure. Software as a Service delivers complete applications through a browser or app. Many real products mix these categories.
Deployment models
Public cloud services are operated by providers and shared across many customers with logical isolation. Private clouds serve one organization. Hybrid cloud combines cloud and on-premises systems, while multi-cloud uses services from more than one provider. The right model depends on compliance, latency, cost, skills, and existing systems.
Regions, availability, and scale
Cloud providers organize infrastructure into regions and availability zones. This helps customers place workloads near users, meet data-location requirements, and design for resilience. Scaling can be fast, but reliability still requires careful architecture, backups, monitoring, capacity planning, and disaster recovery.
Costs and lock-in
Cloud computing can reduce upfront capital spending and speed up experimentation, but it does not automatically lower costs. Usage-based pricing, data transfer fees, overprovisioning, idle resources, and managed-service choices can surprise teams. Switching providers can also be difficult when applications depend deeply on one provider's services.
Why it matters
Cloud computing matters because it changed how software, data, AI, media, commerce, and public services are built and operated. It lets small teams access large-scale infrastructure, gives enterprises faster ways to modernize systems, and supports technologies such as streaming, mobile apps, data analytics, edge computing, and machine learning.