How does Haskell handle overloading polymorphism?

I have a question about Haskell polymorphism.

As I've learned, there are two types of polymorphism:

1. Parametric: where you do not specify the input type.

   Example:

    functionName :: [a] -> a
   

2. Overloading: as imperative programming, i.e. passing different arguments to the same function.

My problem is: how does Haskell handle overloading?