What do people mean when they say they have a portable program? Is it smaller, less files
means it can be run on a portable media (like USB key...), with no install needed; so no track on the hard disk, and no track in the registry...if you're careful. Also useful if you use friend's computers, you can run some apps without installing anything and/or bugging your friends
image editing, not often needed here, but when needed, I use GIMP. It's cool, powerful, and free. To be honest, if I was into serious image editing, I'd buy Photoshop, GIMP can't compare to it, but I'm thankful it exists for the rare times I need to edit a pic.