what does focus do in javascript code example

Example 1: focus js

focusMethod = function getFocus() {          
  document.getElementById("myButton").focus();
}

Example 2: js focus event

const form = document.getElementById('form');

form.addEventListener('focus', (event) => {
  event.target.style.background = 'pink';    
}, true);

form.addEventListener('blur', (event) => {
  event.target.style.background = '';    
}, true);