The public API will give you an easy access to the eZ Publish content repository. This repository is the core component that manages content, locations (nodes in eZ Publish 4.x), sections, content types (Content Classes in eZ Publish 4.x), users, user groups, and roles. It also provides a new, clear interface for plugging in custom field types (datatypes in eZ Publish 4.x).
The public API is built on top of a layered architecture including a persistence API that abstracts storage. By using the public API, you are sure that your code will be forward compatible with future releases based on enhanced, scalable and high-performance storage engines. Applications based on the public API are also fully backwards compatible by using the included storage engine based on the current kernel and database model.