The DOM (Document Object Model) is an API that represents and interacts with any HTML or XML document. The DOM is a document model loaded in the browser and representing the document as a node tree, where each node represents part of the document (e.g. an element, text string, or comment).
The DOM is one of the most-used APIs on the Web because it allows code running in a browser to access and interact with every node in the document. Nodes can be created, moved and changed. Event listeners can be added to nodes and triggered on occurrence of a given event.
DOM was not originally specified—it came about when browsers began implementing JavaScript. This legacy DOM is sometimes called DOM 0. Today, the WHATWG maintains the DOM Living Standard.