A Mean Stack developer specializes in developing web applications using a specific set of technologies - MongoDB, Express.js, Angular, and Node.js, which form the acronym MEAN. They manage everything from the database where data is stored (MongoDB), the server-side operations (Express.js and Node.js), to the client-side user interface and user experience (Angular). They are proficient in JavaScript and JSON, as these technologies support all parts of the MEAN stack. They design, build and maintain web applications, troubleshoot issues, and often collaborate with other team members to integrate different software elements.