MEAN stack is preferred over other stacks because it uses just one programming language, that is, Javascript. MongoDB is a noSQL database that uses commands that are similar to Javascript. Thus, even without learning other languages, you can become a full stack web developer. Javascript is the language over which these frameworks are built on. Though initially used only for front-end development, it later found popularity in server-side scripting as well. MEAN stack and its variants have a huge following and a very active community and is updated regularly. The most popular MEAN variant is MERN stack. ReactJs replaces AngularJs in this variant. Both variations are equally popular and are used by many of the top organizations. That is why they are a good option to learn in a full stack web development course.