In web development, full stack refers to all the layers involved in building a working web application, including data modeling, server, network, user interface, business logic etc. In this module we will focus on the technical layers that are essential for a successful web product, which translates to front end and back end skills.
Go through this very short tutorial for MongoDB here. This 5 minute tutorial will help you understand how MongoDB works as a noSQL DB service.
Even though MongoDB is fast, scalable and easy to use, to make it work with the MEAN stack, we need an object modeling service called Mongoose.
Skim through the Mongoose guide (getting started) here to understand how it works.
Express is a minimal and flexible node.js web application framework, and has become the dominant server-side MVC framework for Node.js. Express defines the responses to each type of HTTP request at each defined route and treats the request and responses as objects you can manipulate in any way you see fitting. You will not be coding anything for Express in this module (already done by MEAN.io). Take a look at it here
Bootstrap is the default front end framework for the MEAN.io project. Though you could switch to other frameworks such as Foundation pretty easily.