This question: AddIn, AddOn and Plugin has been closed.
When I first read it I thought it might be better suited to EL&UEL&U, but since the question is something specific to computer programmes, this seems like it is a good place to ask. It is a useful thing for developers to be able understand the terminology for their own profession.
The question is not vague, incomplete, ambiguous, or overly broad and has been answered in its current form.
Why was this question closed?