With the cloud we can connect large pools of resources via a network, significantly reducing costs if we plan things well, and scaling use to suit our needs. But there differences in public, private or hybrid clouds.

Public clouds are owned by a third party. There is the advantage of sharing in something that has been bought in bulk, reducing costs. There is also the advantage that you only pay for what you use, and you can expand and pay for more use quite quickly. Your customers can also have this advantage, expanding rapidly if needed but only paying for what is actually used. This system is vastly different to the previous non-cloud model where companies had to estimate in advance what storage space was needed; overestimation meant paying for too much, underestimation meant missed opportunities and a mad rush to upscale the operation.
This disadvantage of this public facility was that users had that public’s infrastructure to work within, which may or may not have been what they wanted. However, with multiple third parties offering public clouds companies can usually find one that fits their needs.

Private cloud is built exclusively for an individual enterprise. The company can completely control the infrastructure and resources, and do whatever they wish to handle security. An on-premise private cloud allows complete control of the system, but the physical hardware and its storage capacity have to be estimated and purchased in advance, limiting the fast scalability that was one of the attractions of the cloud in the first place. Still, company employees can share resources and files efficiently.
Externally hosted Private Clouds are hosted by an external cloud provider. Unlike the public cloud there is a fair guarantee of privacy and the infrastructure can be set up to the individual business’s needs.
Hybrid clouds combine the advantages of private and public. Scalability can be external and provided as needed, but the system can use an infrastructure that the business find appropriate. There is more than one type of hybrid, so options vary considerably. It is possible for companies to use a public cloud to spill over any needs not met on their private cloud, and update the private facilities latter on.