Define/Explain the DOM
The Document Object Model (DOM) is an application programming interface (API) that constructs a tree-like structure based on a document (like an HTML document). This allows programming languages and scripts to interact and manipulate elements on the document. The DOM is not a programming language itself, but it's a critical part of website development. As without it, JavaScript would not be able to function correctly. The DOM is not part of JavaScript either, it's a seperate thing that allows JavaScript to work properly.
DOM Specifications
Currently, the Web Hypertext Application Technology Working Group (WHATWG) manages the specifications of the DOM. All standards and specifications of the DOM can be found on their website, as well as other standards they manage. Before the WHATWG, it was the World Wide Web Consortium (W3C) that managed and standarized what the DOM was.
DOM Implementation in Browsers>
When a web browser loads an HTML document, it builds a DOM tree. This DOM tree converts all elements into objects that JavaScript and other languages can manipulate. A DOM tree is structure of nodes, these nodes represent all of the HTML document's content. A single node can represent any part of the HTML document, whether that be a element or comment. The DOM tree is what the browser uses to load HTML documents.
Summary of the Documentation
In short, the Document Object Model is a critical piece of web development. Without, web development would be a whole lot harder. When a browser loads an HTML document, the DOM converts an HTML document's content into workable objects. A DOM is a tree structure of nodes where each node is single piece of an HTML document. The objects can be manipulated with languages like JavaScript in order to create my functionally dynamic web pages. With no DOM, JavaScript could not touch HTML elements to do stuff on them.