Mono.Addins is a generic framework for creating extensible applications, and for creating libraries which extend those applications.
This framework is derived from the add-in engine used by MonoDevelop, although it has been completely rewritten and improved in many ways to make it more generic and easier to use. The MonoDevelop add-in engine was an improvement over the SharpDevelop engine,
which took many ideas from the Eclipse add-in engine.
Mono.Addins has been designed to be useful for a wide range of applications: from simple applications with small extensibility needs, to complex applications (such as MonoDevelop itself) which need support for large add-in structures.
This document includes a detailed description of all features that Mono.Addins provides. If you are interested only in learning what Mono.Addins is about, the document Introduction to Mono.Addins may be more appropriate.