what does locals do in javascript code example

Example 1: localstorage js

// Set
localStorage.setItem('monChat', 'Tom');

// Get
localStorage.getItem('myCat');

// Remove
localStorage.removeItem('myCat');

Example 2: javascript localstorage

localStorage.setItem("user_name", "Bob");

document.body.addEventListener("click", function(){
  alert(localStorage.getItem("user_name"))
});