what are the differences between get_local_mouse_position() and get_global_mouse_position ()?

I am making a bullet-hell game and new to Godot and the forum. I had a problem where the player sprite would rotate relative to the cursor position which made moving awkward, so I made a "gun" Area 2D node that rotates instead of the sprite. However, when I run the game, the gun's origin seems to spawn on the bottom right. I think it may have something to do with get_local_mouse_position() or get_global_mouse position ()? Here is the code:

THE GUN

extends Area2D

var bullet_scene = preload("res://Scenes/Bullet.tscn") ##is the bullet "scene" (object)
func get_input():
	if Input.is_action_pressed("ui_mouse_left"):
		Fire()
		
func _physics_process(delta):
	get_input()
	look_at(get_global_mouse_position())

func Fire():
	var BULLET = bullet_scene.instance() 
	BULLET.position = get_global_position() 
	get_parent().add_child(BULLET)

THE BULLET

extends Area2D

var BULLET_SPEED = 6
var BULLET_POS = Vector2()
onready var CURSOR_POS = null

func _ready():

	CURSOR_POS = get_local_mouse_position() 

func _process(_delta):
	BULLET_POS = BULLET_POS.move_toward(CURSOR_POS,_delta) 
	BULLET_POS = BULLET_POS.normalized()*BULLET_SPEED
	position = position + BULLET_POS