After building a Portable Install you can see what will be installed in the PortableApps folder by looking at the PortableApp directory.  In it, you can see several different files.

• Launcherific.exe is a .NET application that simply launches your application from the settings in the AppInfo\Launcherific.ini file
• Launcherific.exe.config is a required config file that allows Launcherific to run on on any version of Windows from Windows Vista and higher
• The help.html file is generated from the information that was entered in various screens. 
• The other\help directory contains the images and css for the help.html file
• The Data directory should be used to store whatever information is required to be stored for your portable application
• The App\AppInfo directory contains the icons for the PortableApps.com start menu and also the appinfo.ini file required by the PortableApps.com platform
• The App\ProductId directory contains your application

More information on the PortableApps.com Format can be read below

https://portableapps.com/development/portableapps.com_format

 

The installer is actually a .NET Application that is in the PortableBuildInstall directory.  It has the ability to run on any version of Windows from Windows Vista to the current version.