Stands for "Document Object Model."
The DOM is a programming interface for accessing and modifying the content of webpages and XML documents. It defines the logical structure of a document, treating it like a tree where each branching node represents individual elements. Programs and scripts can access the DOM to read and modify the document's structure, content, and style.
The DOM organizes the structure of HTML and XML files in a hierarchy of objects called "nodes." At the root is the Document node, which represents the document as a whole. Next are the Element nodes that represent individual HTML or XML tags. Element nodes are themselves hierarchical in the way that they're nested. For example, the <html> node is closest to the root of the document and contains both the <head> and <body> nodes, and each of those contains child nodes like <div> and <p> elements.