From http://www.w3schools.com (Copyright Refsnes Data)

HTML DOM Introduction

The HTML DOM defines a standard for accessing and manipulating HTML documents.

What You Should Already Know

Before you continue you should have a basic understanding of the following:

HTML / XHTML
JavaScript

If you want to study these subjects first, find the tutorials on our Home page.

What is the DOM?

The DOM is a W3C (World Wide Web Consortium) standard.

The DOM defines a standard for accessing documents like HTML and XML:

"The W3C Document Object Model (DOM) is a platform and language-neutral interface that allows programs and scripts to dynamically access and update the content, structure, and style of a document."

The DOM is separated into 3 different parts / levels:

Core DOM - standard model for any structured document
XML DOM - standard model for XML documents
HTML DOM - standard model for HTML documents

The DOM defines the objects and properties of all document elements, and the methods (interface) to access them.

What is the XML DOM?

The XML DOM defines the objects and properties of all XML elements, and the methods (interface) to access them.

If you want to study the XML DOM, find the XML DOM tutorial on our homepage.

What is the HTML DOM?

The HTML DOM is:

A standard object model for HTML
A standard programming interface for HTML
Platform- and language-independent
A W3C standard

The HTML DOM defines the objects and properties of all HTML elements, and the methods (interface) to access them.

In other words:

The HTML DOM is a standard for how to get, change, add, or delete HTML elements.