Cloud Foundry was mainly developed by VMware and later by Pivotal. As you can see in the following diagram, the basic design is easy to understand. There are different layers of services that are split to scale and communicate between them:

Cloud Foundry provides the ability to run containers independent of the underlying programming language or framework. It provides so-called service brokers that provide a defined connection to existing PaaS solutions from cloud vendors (for example, MySQL from Azure, DB2 from AWS, and so on). It is completely integrated into the CI/CD pipeline of development, and therefore, it has a lot of users from the DevOps parties.