The MERN Stack is similar to the MEAN stack but uses React instead of Angular. It consists of MongoDB, Express.js, React, and Node.js. React, developed by Facebook, is a popular front-end library for building user interfaces with a component-based architecture. The MERN stack leverages React's ability to create fast, dynamic, and interactive user experiences, along with the server-side capabilities of Node.js and Express.js, and the scalable data management of MongoDB. The MERN stack is widely used for developing modern web applications that require rich user interfaces and real-time interactions.