These properties refer to the package locations:

Property NameDescription
OriginalDatabasePoints the path of the current installation package. It can be a location on disk or a location in the Windows Installer cache.
ParentOriginalDatabasePoints the path of the main installation package if the current installation process was launched by a MSI Database Relative to Package or MSI Database with Product Code custom action.
SourceDirPoints the path of the MSI package folder.
TARGETDIRPoints the installation's root destination directory.