The MEAN stack is a set of open-source components that provide an end-to-end framework for building dynamic web applications, consisting of MongoDB as the document database, Express as the back-end web application framework running on top of Node.js, Angular 2 (now known as Angular) as the front-end web app framework, and Node.js as the JavaScript runtime environment. The stack allows developers to implement their application's logic in JavaScript, accessing the database using a native JavaScript/Node.js driver. The MEAN stack is compared to the MERN stack, which uses React instead of Angular. Both stacks are designed to meet the demands of modern web applications, requiring faster development, better performance, and scalability.