A function expression with an internal name, like const greet = function sayHi() {}. The internal name (sayHi) is only visible inside the function, useful for recursion and better stack traces. Outside, you use the variable name (greet).

Because the internal name is available inside the function for self-reference. This is more robust than using the outer variable, which could be reassigned. The internal name is stable and always refers to the function itself.

Yes. The internal name appears in stack traces instead of <anonymous>, which makes debugging easier. This is one reason to prefer named function expressions for critical code paths.