The MERN stack is a powerful technology suite used in app development to build fast, scalable, and dynamic web applications. It includes MongoDB, Express.js, React.js, and Node.js, enabling developers to work entirely in JavaScript on both the front-end and back-end. Join the MERN Stack Course in Chennai at FITA Academy to gain practical skills and become a proficient full-stack developer. React builds UIs, Node.js and Express handle the backend, and MongoDB stores data, making MERN great for web applications.