The first reason is that the prototype property is used by the native constructor functions (e.g., Object(), Array(), Function(), etc.) to allow constructor instances to inherit properties and methods. It is the mechanism that JavaScript itself uses to allow object instances to inherit properties and methods from the constructor function’s prototype property. If you want to understand JavaScript better, you need to understand how JavaScript itself leverages the prototype object.

When creating user-defined constructor functions, you can orchestrate inheritance the same way JavaScript native objects do. But first you have to grok how it works.