The document discusses the MEAN stack, which is a full-stack JavaScript platform for building modern web applications. It is composed of MongoDB (M) as the database, Express.js (E) as the backend framework, AngularJS (A) as the frontend framework, and Node.js (N) as the runtime environment. The document provides descriptions of each component, why the MEAN stack is useful, how to deploy a MEAN application to Heroku cloud, and some tips on getting started and potential limitations.