Cloud services available over the internet to anyone who wants to use them, shared among multiple organizations. Like renting an apartment in a building where multiple tenants share infrastructure.
AWS, Microsoft Azure, and Google Cloud are public clouds where thousands of companies rent computing resources on the same infrastructure.
Public cloud is a deployment model (not a single service). AWS, Microsoft Azure, Google Cloud, and Oracle Cloud Infrastructure (OCI) are all public cloud providers offering shared, multi-tenant infrastructure accessed over the internet with pay-as-you-go pricing.