What is prototype in layman's terms?

The way I understand prototypes:

Javascript is a "classless" object-oriented language, whereas some OO languages such as Java use classes. A class is a static (compile-time) representation of how an object will be eventually realized. Classes are used to describe how an object will inherit properties from other classes.

Now Javascript does not have the class mechanism; objects are just created directly at run-time. In order to give additional properties (and methods) to a new object, you just construct it using the template of an existing parent and then "glue on" additional properties to provide specialization. This scheme is called "prototypal inheritance" and gives Javascript a powerful way to specialize objects as needed. One path of execution may create a specialized property on an object, whereas another path may not.

One secret superpower of prototypal inheritance is to "cache" common methods (functions) between objects efficiently. Instead of having to specify the same function in each object that will use it, you can create a pointer to a function and share it among objects that want to use it. The common function can be maintained in one spot (DRY).

I hope this helps, take care!

-- Calvin