Clicking one element to remove a different element

JavaScript
26

What are the differences between these 2 statements,
and how do you know which one gets used?

  let player = {};
  const lines = document.querySelector(".wrapg .lines");

  let player;
  const lines = document.querySelector(".wrapg .lines");

And I assume I’d be using this one:
let player = {};

I think I understand it now,

Because there’s a statement underneath the “let player,”
then this gets added on next to it = {};

  let player = {};
  const lines = document.querySelector(".wrapg .lines");

But the code works without = {}; added on,
so now I’m not even sure if it’s needed or necessary.

  let player;
  const lines = document.querySelector(".wrapg .lines");