Maybe it wasnt clear what i wrote earlier ill try again sorry.....

I'm trying to learn to use 'Managed Extensibility Framework' aka 'MEF' to create an application which i can add extensions (i think thats obvious )

its using interfaces and implementations to use code from a method hard-coded/loaded as if it was a part of the main program itself. basically its a way of adding any code you want to a program at run-time.
i just need a little guidence regarding 'interfaces and implements' keywords, and how i need to use them with the MEF

second, the imports and exports keywords used with MEF, which basically need to match up to allow the main program to run added modules, i just need a little help understanding the syntax.

any help would be appreciated, the sample project im learning with is 'SimpleCalculator MEF tutorial' at microsoft.com

thanks