class
A class contains rules which define the behavior of your application. You can create classes to gather rules related to a specific object in your application. For example, in a recruitment application, you can create a class that contains rules defining the flow of recruitment process. Classes can contain other classes, hence a class that contains another class is called a parent class, while a class that is contained by another class is called a child class. A child class can reuse, or inherit, any of the rules defined for its parent class what helps to build your application faster and more efficiently.