This document discusses the server roles and architecture of a SharePoint 2010 web application. It describes the roles of the web front end server, application server, and SQL server. It explains that some resources like core pages and controls come from the file system, while others like list items and documents come from the SQL database. It also notes that modifying files that ship with SharePoint is not supported and can lead to out-of-sync servers, and that custom files should be added through solution packages instead of directly to the SharePoint root.