The document provides an overview of the Client Side Object Model (CSOM) in SharePoint 2013. It discusses how CSOM allows code to run outside the SharePoint server and enables client-side development. New features in SharePoint 2013 include expanded CSOM coverage, support for REST and OData, and the ability to build SharePoint apps using only client-side code. The document also outlines common CSOM tools and libraries like jQuery, DataJS, Knockout, and debugging tools like Fiddler and Firebug.