I created this visual representation of the deployment models to give a bit more insight from the business perspective. There is a Services layer (Web and Business Services) which are or could be made available in each deployment model and for the existing systems. Accessing these Services to build additional application and business functionality is a tremendous benefit. You can maintain existing systems, add in new cloud services and functionality exposed via services and create new value for the business quickly and efficiently.
- Public Cloud. The cloud infrastructure is made available to the general public or a large industry group and is owned by an organization selling cloud services.
- Private Cloud. The cloud infrastructure is operated solely for an organization. It may be managed by the organization or a third party and may exist on premise or off premise.
- Hybrid Cloud. The cloud infrastructure is a composition of two or more clouds (private, community, or public) that remain unique entities but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load-balancing between clouds).
- Community Cloud. The cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, and compliance considerations). It may be managed by the organizations or a third party and may exist on premise or off premise.
–Definitions are from NIST Definition of Cloud Computing. Version 15