The 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 standard is separated into 3 parts:
Core DOM: The standard model for all document types.
XML DOM: The standard model for XML documents.
HTML DOM: The standard model for HTML documents.
For example, given this HTML:
<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>
</head>
<body>
<h1>A Heading</h1>
<p>A Paragraph</p>
</body>
</html>
We can refer to DOM as document.head or document.h1 and so on.