Components and Confusion in Facelets

The word component is used a lot in Facelets (and supporting technologies):

• Facelets Custom Tag
• Specially packaged ui:components or ui:compositions.
• Facelets ui:component 
• essentially just a ui:composition with a backing bean.
• Driven by xhtml with more tags.
• JSF Custom UI Components
• Subclasses of javax.faces.component.UIComponent.  
• Driven by Java backing beans (rendered as HTML via a renderer)
• backing beans are different from managed beans
• Creates a new tag to be used with xhtml.
• JSF Advanced Composite Components
• They're like a template (in the generic sense, not a ui:template).
• They mean the UIComponents not the ui:components
• JSP Custom Tags
• From Java5, obsolete to a JSF application.
• Mentioned in passing in Java6 docs.
• Also creates a new tag to be used with xhtml.

In general if you're talking about facelets, a component is a ui:component and a custom tag is a facelets custom tag.  If you're talking about JSF, a component is a UIComponent and a custom tag is a JSP custom tag.

Further more, this shouldn't be confused with general purpose software components, strict components, or modules.