What is MEF (Manage extensibility framework)?
MEF is a framework by which you can make your application extensible. For example you have an accounting application and you would like to provide a hook (socket) where external vendors can connect (plug) and add invoicing capabilities to the accounting application. For instance you have application which you would want different vendors to connect with their features and extend your application. So the vendors just put the components in the application, the application discovers them and does the connection and extension.
