The handle is a Java object running at the server, with which the application access. From application's viewpoint, it is everything about a component, so, in the context of application development, we usually just call it a component rather than separating the concept of view and handle.

The handle must implement two interfaces: org.zkoss.zk.ui.Component and org.zkoss.zk.ui.sys.ComonentCtrl. Component is a collection of APIs that applications could access, while ComponentCtrl is a collection of APIs that are accessible only by ZK and component development.

However, you generally don't implement them from scratch. Rather, you pick up one of skeletal implementations or an existent component that fulfill your requirement, and then extend from them. The following section describes each of these skeletal implementations.