In a general term, cloud computing can be defined as anything that aims to deliver hosted service over the internet. It can also be termed as, a way to use a virtual computer exactly with the same personalized experience irrespective of global position. In general, cloud services are divided into three basic categories: IaaS (Infrastructure-as-a-Service), PaaS (Platform-as-a-Service) and SaaS (Software-as-a-Service). The cloud symbol inspired the name "Cloud Computing" which stands to represent the internet in flowcharts and diagrams.
Three distinct characteristics of a cloud service have differentiated cloud from traditional hosting services. Cloud computing service is elastic, and it is sold on demand. A user can have this service according to his requirement. To satisfy the demand users can have it by the minute or the hour. To use this service consumers only require a PC with internet connection, and this service is fully managed by the provider. The cloud services getting accelerated interests due to significant innovations in distributed computing and virtualization. Fairly speaking, high speed internet connection as well as the weak economy has also a great part to accelerate interests.
IaaS ensures virtual server instance API to start, stop, configure and access to virtual storage and servers. Amazon Web Services could have been a great example of IaaS. It is also termed as utility computing. In case of the enterprise, a company is allowed to use as he requires, and they have to pay accordingly. You can also say that it is a pay-for-what-use model, which looks like the way water, fuel and electricity are consumed.
In the cloud system, PaaS can be defined as a set of product development tools and software which are hosted on the infrastructure of providers. Here, developers use internet connection to create applications on the provider's platform. The providers of PaaS system can use website portals, APIs and installed gateway software on the consumer's PC. GoogleApps and Force.com are two examples of the PaaS cloud computing system.
In case of SaaS cloud computing system, the vendor interacts with the users through a front-end portal and supplies both hardware infrastructure and software. SaaS holds a broad web-market, and here service can be anything from database processing to inventory control and Web-based email.
A cloud service can be categorized as public and private services. A Public cloud supplies rented services to anyone on the internet, but a private cloud supplies hosted services to a limited number of customers. As an example: Amazon Web Services is the largest public cloud provider of recent time. If a service provider uses the resources of public cloud to make their private cloud, then the service is called as virtual private cloud. Cloud computing service aims to provide IT services and computing resources to customers, and it does not matter whether it is private or public.
Source by Ananta Modak