The word polymorphism comes from the Greek polys (many, much) and morphē (form, shape), and its meaning is the provision of a single interface for entities of different types.

In our car example, we call engine.start(), regardless of what kind of engine it is. As long as it exposes the start method, we can call it. That's polymorphism in action.

In other languages, such as Java, in order to give a function the ability to accept different types and call a method on them, those types need to be coded in such a way that they share an interface. In this way, the compiler knows that the method will be available regardless of the type of the object the function is fed (as long as it extends the proper interface, of course).

In Python, things are different. Polymorphism is implicit, nothing prevents you from calling a method on an object; therefore, technically, there is no need to implement interfaces or other patterns.

There is a special kind of polymorphism called ad hoc polymorphism, which is what we saw in the last paragraph: operator overloading. This is the ability of an operator to change shape, according to the type of data it is fed.

Polymorphism also allows Python programmers to simply use the interface (methods and properties) exposed from an object rather than having to check which class it was instantiated from. This allows the code to be more compact and feel more natural.

I cannot spend too much time on polymorphism, but I encourage you to check it out by yourself, it will expand your understanding of OOP. Good luck!