Abstract Class

An absrract class is a special kind of class that cannot be instantiated. So the question is why we need a class   that cannot be instantiated? An absrract class  is only to be sub-classed (inherited from). In other words, it only allows other classes to inherit from it but cannot be instantiated. The advantage is that it enforces certain hierarchies for all the subclasses. In simple words, it is a kind of contract that forces all the subclasses to carry on the same hierarchies or standards.