Catalog File is txt file with a set of package for install..
With it you can install applications with one-click. The catalog feature its part of PackageKit
create a file, save with .catalog extension
[PackageKit Catalog] InstallPackages(foresight)=group-gnome-devel-dist
So when you click on it. PackageKit Know what you need install group-gnome-devel-dist...
You can add more packages
[PackageKit Catalog] InstallPackages(foresight)=christine InstallPackages(foresight)=gnome-mplayer
Remember the package you added must be on the actual branch you have ( fl:2 , fl:2-qa , fl:2-devel )
MoreInfo: http://packagekit.org/pk-faq.html#catalogs