The DOM, or Document Object Model, is basically how the browser turns a web page into something it can actually work with. Instead of just reading raw HTML, the browser builds the page into a structured tree of elements. That structure lets JavaScript go in and grab things, change text, add new content, or remove stuff completely. Without the DOM, web pages would just sit there and not really do anything interactive.
The DOM follows official web standards so everything works consistently. It originally came from the W3C, which created the early versions of the DOM. Now it is mainly maintained by WHATWG as a living standard. These specifications define how elements, nodes, and events should behave, which makes it possible for developers to write code that works the same way across different browsers.
Each browser has its own engine, but they all follow the same DOM rules. When a browser loads a page, it reads the HTML and builds the DOM tree behind the scenes. That tree is what gets displayed on the screen and what JavaScript interacts with. Even though Chrome, Firefox, and Safari use different engines, they try to follow the same standards so everything behaves the same for users.
Overall, the DOM is a key part of how modern websites work. It gives structure to a page and lets JavaScript control and update content. The standards behind it came from the W3C and are now maintained by WHATWG, and browsers implement those standards so developers can build interactive websites that work across the web.