KnockoutJS is a JavaScript framework that uses a Model-View-View Model (MVVM) pattern to build quick, single-page applications. The document introduces KnockoutJS and how it can be used to build a simple, fast contact viewer using JavaScript remoting. It discusses how the view model contains observables that the view can bind to, and when their values change, the view automatically updates. Resources for learning more about KnockoutJS are provided.