app

The app is the base of everything. below that you can only call something like a root level. The "scripting engine" alert($.locale). Don't worry about that. You can use this to get output in the ESTK like this:

    $.writeln("Hello World")

But this is only for debugging. So the app holds documents, fonts, selection and things like this.

    /**
    Get he app version like this  
    */  
    alert(app.name + " v" + app.version);  

Or you could use the selection like this.

    /**
    You need a page and a selected item to run this script
    */
    alert(app.selection[0].constructor.name)

    /*
      You can adress a target application like this
    */
    #target indesign
    alert(app.colorSettings.properties.toSource());