Cloud computing is the on-demand delivery of computing services—including data storage, servers, databases, and networking—over the internet on a pay-as-you-go basis.

Physical infrastructure consists of tangible hardware components like servers, routers, cables, and data centers that house and power computing systems.

Virtual infrastructure consists of software-based resources—such as virtual machines, virtual networks, and storage—abstracted from underlying physical hardware using hypervisors.

Physical infrastructure is hardware-dependent, rigid, and costly to scale, whereas virtual infrastructure is software-defined, flexible, and instantly scalable without buying new hardware.

Cloud infrastructure is a combination of physical hardware and virtualization software managed by a provider to deliver scalable computing resources over the internet.