Interface: does not have implementations. Its just a contract between user and provider.So in layman's words it just contains function signature :NO Implementation No data Members Abstract Class:contains one or more virtual function.. Cannot be instantiated, Might have data members and implementation of few functions... made to be inherited Virtual class: can have data,can have implementation of functions... only difference is if inherited twice (thru two paths) the subclass gets only one copy of the data members,hence avoiding ambiquity