By Defination, “Cloud Computing is the practice of using a network of remote servers hosted on the Internet to store, manage, and process data, rather than a local server.””

“Cloud means network of networks providing remote access to set of decentralized IT resources.”

”.. a style of computing in which scalable and elastic IT-enabled capabilities are delivered as service to external customers using internate technologies.”

“… a standardized IT capability (services, software, or infrastructure) delivered via internat technologies in a pay-per-use, self service way.”

Capacity planning, cost reduction, and organizational agility are primary features that exposed the need for cloud computing.

A Cloud service is any IT Resouces that is made remotally accessible via a cloud.

An on the premises network (within an organization boundary) of a controlled IT environment is not a cloud.

There can be two type of scaling on cloud

1. Horizontal Scaling (Resource out and in)
2. Vertical Scaling (Resource up and down)

Three common cloud delivery models:

1. Infrastructure as a service (IaaS)
	This can include hardware, network, connectivity, operating system and other raw IT Resources. 
2. Platform as a service (PasS)
	This represents a "ready to use" environment.
3. Software as a service (SasS)
	A software product or utility deplyed as a share cloud service.

More common deployment models are :

1. Public clouds
2. Community clouds
3. Private clouds
4. Hybrid clouds

For Other basics about cloud like Data Center Technology, Virtualization Technology, Web Technology, Multitenant Technology, Services Technology please check out the What is cloud for more quick reference site.