Abstract methods – abstract classes.

That is, the driver moves only Cars, Bicycles, but not a "Vehicle". In fact the Vehicle class does not need to define the move() method.

Similarly a Ring class does not need to define addition and multiplication. (But it is obvious, that a Ring has addition, multiplication, etc.)

The object oriented paradigm allows to declare a method in a class without implementing it. This is the concept of abstract classes.

That is, the driver moves only Cars, Bicycles, but not a "Vehicle". In fact the Vehicle class does not need to define the move() method.