For example, mountain bikes, racing bikes, and tandems are all different kinds of bicycles. In object-oriented terminology, mountain bikes, racing bikes, and tandems are all subclasses of the bicycle class. Similarly, the bicycle class is the superclass of mountain bikes, racing bikes, and tandems. Also, each subclass inherits methods from the superclass. However, subclasses are not limited to the state and behaviors provided to them by their superclass.
Subclasses can add variables and methods to the ones they inherit from the superclass.
Subclasses can also override inherited methods and provide specialized implementations for those methods. You are not limited to just one layer of inheritance. The inheritance tree, or class hierarchy, can be as deep as needed. Methods and variables are inherited down through the levels. In general, the further down in the hierarchy a class appears, the more specialized its behavior.