so if you apply for a job that has that line as a requirement what exactly are you supposed to know about inheritance, polymorphism and encapsulation?
Do you think it's about reciting definitions or just being aware of the fact that in OO languages such as C# it is possible to implicitly convert an expression of a derived type to an expression of a base type and explictly perform the reverse operation, as well as have derived classes that have members with the same name but different functionality?
No idea about what exactly is understood by the term encapsulation. (I don't know the dictionary definition though I might be aware of the concept). Does it have to do with taking the implementation of a type/type member away from the user as much as possible? Or is it about an expression of a base type 'encapsulating' an expression of a derived type?