In brief, MVC is a programming design pattern for separating the different concerns of your application. The M corresponds to Model and is used to define domain object. The V corresponds to View and is responsible for display logic. Finally, the C corresponds to Controller and is responsible for user interactions and interactions between Views and Models.
You can find source code of the application here https://github.com/shekhargulati/getbookmarks. Backbone.js is used by Linkedin, Foursquare, Wunderkit, Groupon, etc to build complex applications. You can view the full list here.