Plug-in Extension Points
Extension points define new function points for the platform that other plug-ins can plug into. The Extension Points page is the place to add, remove and edit extension points declared by your plug-in.
An extension point has three attributes:
ID - a required attribute whose value is a simple name
Name - a required attribute whose value is a translatable string
Schema - an optional attribute whose value is a relative path to the schema corresponding to this extension point
Although the Schema attribute is optional, you are strongly encouraged to provide a schema; since, PDE utilizes it to assist other developers in using your extension point.