With a public cloud, services are delivered to customers over a network that's open for public usage. Public clouds offer efficiency and affordability and are often multi-tenant meaning the provider runs your service in a shared environment.
With a private cloud, services are maintained on a private network protected by a firewall. You can build a private cloud within your own data centre or subscribe to one hosted by a vendor. Private clouds offer the most security and control.
A hybrid cloud is a composition of two or more clouds often from multiple providers. Hybrid clouds offer variety, so you can pick and choose which aspects of your business to include in a hybrid landscape, a build of both cloud and on-premise.