Cloud Computing is the general term for everything involved in delivering hosting services over the Internet. Cloud computing relies on sharing of resources to achieve coherence and economies of scale, similar to a public utility.
These services are broadly divided into three categories:
“Infrastructure as a service” refers to online services that provide high-level APIs used to dereference various low-level details of underlying network infrastructure like physical computing resources, location, data partitioning, scaling, security, backup etc. Pools of hypervisors within the cloud operational system can support large numbers of virtual machines and the ability to scale services up and down according to customers’ varying requirements.
PaaS vendors offer a development environment to application developers. The provider typically develops toolkit and standards for development and channels for distribution and payment. In the PaaS models, cloud providers deliver a computing platform, typically including operating system, programming-language execution environment, database, and web server.
In the software as a service (SaaS) model, users gain access to application software and databases. Cloud providers manage the infrastructure and platforms that run the applications. SaaS is sometimes referred to as “on-demand software” and is usually priced on a pay-per-use basis or using a subscription fee. In the SaaS model, cloud providers install and operate application software in the cloud and cloud users access the software from cloud clients. Cloud users do not manage the cloud infrastructure and platform where the application runs.
The cloud computing name was inspired by the cloud icon that was often used to introduce the Internet into block diagrams.
Cloud service has three features that distinguish it from traditional hosting.
Selling on demand – usually within minutes or hours.
Elasticity – the user can have as many or as few services as they want within the given time.
The service is completely managed by the provider (the user remains solely for the computer and access to the Internet).
Cloud computing can be private or public. The public sells services to anyone on the Internet while it is owned by a network or data center that supplies hosting services to a limited number of people.
However, private or public cloud computing, the goal is to provide easier access to computer resources or information technology services.