The cloud infrastructure is operated exclusively by an organization. It can be administered by the organization or a third party and may exist premise or off premise.
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 can be managed by organizations or third parties and may be premise or off premise.
Cloud Infrastructure is available to the general public or a group of large companies and is owned by an organization selling cloud services.
Cloud infrastructure is a composition of two or more clouds (private, community or public) that remain unique entities but are linked together by standard or proprietary technology that enables data and application portability.