Cloud computing is a term for computing resources and services such as server and network infrastructure, web servers, and databases, hosted by cloud service vendors, rented by tenants, and delivered via the Internet.

Cloud computing companies such as Microsoft and Google offer a variety of computing services built on top of their own infrastructure, which are managed in dedicated globally distributed data centers that offer high availability, resilience, and scalability.

There are three types of cloud service models, Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). IaaS is the lowest service tier that offers server, storage, and networking infrastructure, which users can build their own systems on. PaaS allows users to create and deploy applications without having to worry about the infrastructure that's hosting it using services and tools designed to streamline the development and deployment processes. SaaS offers on-demand software products, which remove the infrastructure and software installation and setup overhead; web mail providers are an example of SaaS, where users can send and receive mails using a website rather than having to install a mail client on their machine.

Cloud services are often a cost-effective alternative to traditional on-premises infrastructure, which requires an initial investment in hardware and licenses and requires continual maintenance and expansion as required as well as utility costs such as premises' rent, electricity, and ISP.

There are four main cloud deployment models: public cloud, private cloud, hybrid cloud, and community cloud. Public cloud services are hosted by a vendor and made available to the public for use. Private cloud services emulate public cloud services in terms of features but are only available within a company's domain. Community cloud is a private cloud shared between a number of users. Hybrid cloud is a mixture of the other three.