an application that exposes a programmable object to another application
an application that exposes its functionality for client applications, called Automation controllers, to use
an application that exposes programmable objects to other applications
An application that can be driven by other applications via Automation. An Automation server application has exposed its functionality so that other applications can access its functionality in custom solutions. For example, Microsoft Access is an Automation server that exposes its forms and reports so that they can be used from other applications.