What do the two symbols => in a row mean

Question

I know lambdas and function like type, but what is this:

displayFunc: (string) => string = x => x;

Two symbols "=>" confuse me. What is the result?

Answer 1

One is type the other one is implementation.

type MyFunctionType = (string) => string

const displayFunc: MyFunctionType = x => x;

/// OR

const displayFunc: MyFunctionType = function(x: string): string {
  return x;
};

(string) => string means a function type that takes string and returns string;

x => x is an identity function, meaning it returns the same thing it was passed in.