Cloud computing, often referred to as simply "the cloud" is the delivery of on-demand computing resources, everything from applications to data centers, over the Internet on a pay-for-use basis. Cloud computing enables companies to consume compute resources as a utility, rather than having to build and maintain computing infrastructures in-house.
Cloud Computing benefits
Self-service: End users can spin up computing resources for almost any type of workload on-demand. In other words, all the IT resources you need with self-service access.
Elastic resources: Companies can scale up or down quickly and easily to meet demand.
Pay for use: Metered service so you only pay for what you use.
Cloud Computing services
Software as a service (SaaS): Cloud-based applications/software as a service (SaaS) run on distant computers "in the cloud" that are owned and operated by users and that connect to their computers/mobile via the Internet and, usually, a web browser. These are often called Web services.
Platform as a service (PaaS): It provides a cloud-based environment with everything required to support the complete lifecycle of building and delivering web-based (cloud) applications without the cost and complexity of buying and managing the underlying hardware, software, provisioning and hosting.
Infrastructure as a service (IaaS): It provides companies with computing resources including servers, networking, storage, and data center space on a pay-per-use basis, for various workload needs.
Cloud Computing deployment models
Public cloud: Public clouds are owned and operated by companies that use them to offer rapid access to affordable computing resources to other organizations or individuals. With public cloud services, users don't need to purchase hardware, software or supporting infrastructure, which is owned and managed by providers.
Private cloud: A private cloud is owned and operated by a single company that controls the way virtualized resources and automated services are customized and used by various lines of business and constituent groups. Private clouds exist to take advantage of many of cloud's efficiencies, while providing more control of resources and steering clear of multi-tenancy.
Hybrid cloud: A hybrid cloud uses a private cloud foundation combined with the strategic use of public cloud services. The reality is a private cloud can't exist in isolation from the rest of a company's IT resources and the public cloud. Most companies with private clouds will evolve to manage workloads across data centers, private clouds and public clouds—thereby creating hybrid clouds.