The document discusses web parts in SharePoint. It defines web parts as small chunks of user interface and functionality that can be aggregated together to build page content. Web parts allow end-users to add, remove, and determine the placement of web parts on a page. The document then covers the history of web parts in SharePoint and ASP.NET, how to work with and build web parts, deploying web parts, using web parts in sandboxed solutions, visual web parts, web part properties, and creating connectable web parts.