The MERN stack is a robust set of four technologies used for building full-stack web applications: MongoDB, Express.js, React.js, and Node.js. It enables developers to use JavaScript throughout the entire development process, from front-end to back-end. MongoDB manages the data, Express and Node handle the server-side logic, while React is used for creating responsive user interfaces. MERN streamlines development, making it easier to create fast, modern web applications. Enroll in a MERN Stack Course in Chennai at FITA Academy to gain expert guidance and hands-on experience, helping you master full-stack web development.