Basically, there are three types of clouds in cloud computing, they are public, private and hybrid clouds. 

In a public cloud, third-party service providers make resources and services available to their customers via the internet. The customers' applications and data are deployed on infrastructure that is owned and secured by the service provider.

A private cloud provides many of the same benefits of a public cloud but the services and data are managed by the organization, or a third-party, solely, for the customer's organization. Usually, a private cloud places increased administrative overheads on the customer but gives greater control over the infrastructure and reduces security-related concerns. The infrastructure may be located on or off the organization’s premises.

A hybrid  cloud is a combination of both a private and a public cloud. The decision on what runs on the private versus the public cloud is usually based on business criticality of the application and sensitivity of the data. But in some cases, spikes in demand for resources, or spillovers, in the private cloud are also handled in the public cloud.