The DOM (Document Object Model) is a cross-platform and language-independent interface that treats an HTML or XML document as a tree structure where each node is an object representing a part of the document. This hierarchical structure allows programs and scripts to dynamically access and update the content, structure, and style of a document. The DOM is essential for web development, enabling JavaScript to interact with web pages, manipulate elements, handle events, and create dynamic content. It is a core technology for building interactive and responsive web applications.