The MERN Stack is a popular web development framework that consists of four main technologies: MongoDB, Express.js, React, and Node.js. Each component plays a specific role: MongoDB is a NoSQL database that stores data, Express.js is a web application framework for building APIs, React is a JavaScript library for creating user interfaces, and Node.js allows developers to run JavaScript on the server side. This stack enables developers to build full-stack applications using JavaScript throughout the entire development process. By using the MERN Stack, developers can create dynamic and responsive web applications efficiently, as it allows for seamless integration between the front-end and back-end components.