Definition: As defined by NIST(national institute of technology) Cloud computing is essentially on demand access to computing resources.
It has essential characterstics of on demand self service, resource pooling, rapid elasticity to scale out and scale in, the ability to meter who is using what and broad network access.
Three service models for cloud computing are:
1. SaaS software as a service, is a prebuilt, vertically integrated application/solution delivered to customer as a service.
2. IaaS infrastructure as a service, is purely providing computing resources, storage and network, as service to the client.
3. PaaS platform as a service. is a flexible combination of above two service models and thus customer can develop and deploy their own application using best of both the worlds.
Deployment models:
1. Public cloud, is shared across multiple customers or tenants and is hosted and managed by a service provider.
2. Private cloud on the other hand is exclusive for an organization and is controlled and governed by that organization.
3. Hybrid cloud is where an organization with a private cloud model uses public clouds for any excess cloud service requirements occassionally. Eg an overflow or for additional workload needs
4. Community cloud is a semi private cloud with access to only a set of defined tenants who share backgrounds or needs
What is driving clouds ?
AGILITY AGILITY AGILITY
The fact that users can provision resources on demand, acquire more resources when needed and release them when done with them, is the key driver for cloud computing.
Any drop off which may occur in the interaction happening between two clouds, might just mean a complete loss of valuable services. It is like two clouds up in the sky and informatiin flashin like lightening going from cloud to cloud and cloud to ground, the possibiltiess of loss of energy is inevitable and that is where the core problem of cloud computing lies.
Amazon web services are already in this niche market. For a public cloud to become a feasible solution for small businesses, the need to ensure the security of transaction and data.
Google OS is another such initiative where we will see a huge participation and usage of cloud computing capabilities.
Oracle E-Business Suite 12.1.1 in a five-part nutshell. 
