Backbone is a minimal JavaScript library that provides a Model-View-Controller structure for building web applications. It includes Models for managing data, Views for displaying UI, and a Router for handling application state. While it handles core functions like syncing data and delegating events, it does not include features like automatic data binding or template rendering. Models use methods like fetch(), save(), and destroy() to work with data, and can be organized into Collections. Views create DOM elements and delegate events to associated functions. Backbone keeps file sizes small and avoids complexity, making it suitable for mobile development.