What is Cloud Computing?
On-demand delivery of compute, storage, and services over the internet, billed by consumption.
Definition
Cloud computing replaces capital expenditure on hardware with operational expenditure on rented capacity, provisioned via API in seconds rather than procurement cycles in weeks. The service models form a ladder of ceded responsibility: IaaS gives you virtual machines and networks, PaaS abstracts the operating system, and SaaS delivers the finished application. AWS, Azure, and Google Cloud dominate, with the shared responsibility model dividing security duties—the provider secures the infrastructure, you secure what you deploy on it. The economics reverse at scale: elasticity is a bargain for variable workloads and can be markedly more expensive than owned hardware for steady ones, which is what drives periodic repatriation decisions and multi-cloud hedging against lock-in.