JSF provides automatic integration between user interface components and model objects, which are typically implemented as JavaBeans. These objects live in some scope of the application, such as request, session, or application. JSF allows you to configure beans in its configuration file (faces-config.xml) so that they are automatically created the first time they are referenced. This saves you the trouble of creating beans via JSP usebean tags or in Java code.

To be more specific, JSF has a dependency injection container called the Managed Bean Creation Facility (MBCF). Any object created by the MBCF is called a "managed bean". Usually, most of the objects used in your application will be managed beans (or they will be managed by another dependency injection container, such as Spring).