The Fission Theory: This theory proposes that the Moon was once part of the Earth and somehow separated from the Earth early in the history of the solar system.
This provides modular approach to programming. Classes. A class is a concept used in object oriented programming languages such as C++, PHP, and JAVA etc. Apart from holding data, a class is also used to hold functions. An object is an instant of a class. In case of variables, the type is the class whereas the variable is the object.
A class is a blueprint or template or set of instructions to build a specific type of object. Every object is built from a class. Each class should be designed and programmed to accomplish one, and only one, thing. (You'll learn more about the Single Responsibility Principle in Object-oriented programming concepts: Writing classes.)