After you create your first IntraWeb Application using the IntraWeb Wizard, we will give you a brief explanation of the created files.
This is the main file of your project, as any Delphi application.
This is the "central" part of your application. It contains the definition of the ServerController class, which basically manages all the user sessions, creating and destroing them and also it is the point the developer can enhace/modify application responses, through the ServerController events, like OnBeforeDispatch and others (see more details on the ServerController class description).
The TIWUserSession class is inherited from TDataModule and you will use it basically for storing and manipulating all the informations related to a user session. You can, for example, use the User Session to expose datasets, classes and business rules from your previous Dekstop applications.
In general, you have only one TIWUserSession class definition, but you may have other TIWUserSession definitions in your application, for modularization purposes.
As the VCL/FMX applications, IntraWeb has it's own form for building the User Interfaces for yout Web Applications and it is here that you add the IntraWeb and 3rd-party visual components to build your user interface, as well some non-visual components. You usually will have several IWForms in your Web Applications. You can add more IWForms to your application opening the IntraWeb Wizard and choosing New Form from the IntraWeb options.