Definition - What does Public Cloud mean?
Public cloud refers to a computing service model used for the provisioning of storage and computational services to the general public over the internet.
Public cloud facilitates access to IT resources on a "pay as you go" billing model. A service provider manages a public cloud solution's core infrastructure, software and other back-end architecture in a multitenant environment in order to free up the customer from these responsibilities.
Techopedia explains Public Cloud
Public cloud is what most people refer to when they say "cloud computing." The term is almost redundant as, by definition, something on the cloud is generally available.
There is however a differentiation between the public cloud and private cloud. The delivery model of a private cloud is pretty much the same – it is still cloud computing. However, the services in a private cloud are provided behind a firewall and are only accessible to the users or partners of a single organization. A company would do this to take advantage of virtualization and the centralization that cloud computing provides but without the potential security problems that arise from dealing with a public cloud vendor.