Creating and Using Custom Components - Visualforce

Up until this point you’ve been using standard Visualforce components, such as <apex:dataTable>. Visualforce has dozens of these components, but sometimes you’ll want to create your own. For example, you might want to encapsulate your own custom markup and behavior, which you can reuse on many different Visualforce pages.

Unlike the templates in Tutorial #9: Reusing Pages with Templates, custom components can have their own attributes that can change their appearance on the page in which they’re embedded. They can also have complex controller-based logic that executes for that instance of the component. Custom components also automatically become part of the Component Reference help. In short, custom components let you extend Visualforce in whichever direction you see fit.