The global variable Application, of type TApplication, is in every VCL-based application. Application encapsulates your application as well as providing many functions that occur in the background of the program. For instance, Application handles how you call a Help file from the menu of your program. Understanding how TApplication works is more important to a component writer than to developers of stand-alone applications, but you should set the options that Application handles in the ProjectOptions Application page when you create a project. 

In addition, Application receives many events that apply to the application as a whole. For example, the OnActivate event lets you perform actions when the application first starts up, the OnIdle event lets you perform background processes when the application is not busy, the OnMessage event lets you intercept Windows messages (on Windows only), the OnEvent event lets you intercept events, and so on. Although you can't use the IDE to examine the properties and events of the global Application variable, another component, TApplicationEvents, intercepts the events and lets you supply event-handlers using the IDE.