JavaServer Faces technology offers the concept of composite components with Facelets. A composite component is a special type of template that acts as a component.

Any component is essentially a piece of reusable code that behaves in a particular way. For example, an input component accepts user input. A component can also have validators, converters, and listeners attached to it to perform certain defined actions.

A composite component consists of a collection of markup tags and other existing components. This reusable, user-created component has a customized, defined functionality and can have validators, converters, and listeners attached to it like any other component.