Package definition files are predefined scripts that you can use to help automate package creation with Microsoft System Center Configuration Manager 2007. These are files that contain the package and program information needed to distribute a package to clients, with the exception of the source file location.
Package definition files often come with an application's source files or are available from the application's developer. Configuration Manager 2007 also has a selection of package definition files that are automatically imported and available in the Create Package from Definition Wizard.
You can also import Windows Installer files with .msi extensions and Configuration Manager 2007 can build packages from the Windows Installer information.
For more information about the format of these files, see About the Package Definition File Format.