The document defines the Document Object Model (DOM) as an application programming interface (API) for HTML and XML documents that defines the logical structure of a document and how it can be accessed and manipulated programmatically. The DOM is a W3C standard separated into three parts - the core DOM for any structured document, the XML DOM for XML documents, and the HTML DOM for HTML documents. The DOM provides a standard programming interface that can be used across various environments and applications to dynamically access and update the content, structure, and style of documents.