js hoisting some variables are accessible others are not?

Question

 function openMenu() {
  var menu = document.getElementById("menu")
  var num = 123
  menu.classList.remove("hidden")
}

function closeMenu() {
  menu.classList.add("hidden")
  console.log(num)  
}

https://jsfiddle.net/kn5ateov/

I thought i knew hoisting, now I know, I know nothing. How come the second function has access to the var menu but not the var num?