The way each document objects or nodes are manipulated by programming languages is DOM. Dom is the fully object oriented representation of HTML document.
###What is the difference between == and ===?
== is equal value and === is equal value and eaqual type e.g.http://www.w3schools.com/js/js_comparisons.
It is the rectangular boxes that are generated to each elements in the DOM tree, comprises of height, width, padding, margin, border.
When you execute something synchronously, you wait for it to finish before moving on to another task. When you execute something asynchronously, you can move on to another task before it finishes.