MEAN is a free and open-source JavaScript software stack for building dynamic web sites and web applications. The MEAN stack is MongoDB, Express.js, AngularJS, and Node.js.
A number of variations on the traditional MEAN stack are available by replacing one or more of the components with similar (typically Javascript-based) frameworks. For example: In a MEEN stack, the JavaScript MVC framework Ember.js is used instead of Angular, and likewise for the MERN stack, where React.JS is used as a substitute.