Cloud computing is the on-demand delivery of IT resources over the Internet with pay-as-you-go pricing, fundamentally changing how organizations access and manage technology infrastructure. Rather than investing in and maintaining physical data centers, organizations can provision compute, storage, databases, and other services instantly from cloud providers like AWS, Microsoft Azure, and Google Cloud Platform. The key mental model: cloud computing shifts IT from a capital expenditure (buying servers) to an operational expenditure (renting capacity), enabling unprecedented agility, scalability, and cost efficiency while letting teams focus on innovation rather than infrastructure management.