A MEAN Stack Developer is a professional who specializes in using a specific set of technologies - MongoDB, Express.js, Angular, and Node.js, which form the acronym MEAN. They create end-to-end web applications. They design and build the database using MongoDB, manage the server and routing with Express.js, handle the client-side of applications with Angular, and use Node.js for server-side execution. They are responsible for developing, testing, and maintaining web applications, ensuring smooth communication between different systems, and troubleshooting issues. They also collaborate with other developers and professionals, providing efficient web solutions.