Things that J has and F doesn't. Auto head lamp capability, power mirrors, electronic vehicle information center capability, homelink capability, keyless go, illuminated cup holder and door pull capability, rearview mirror auto dimming capability, steering wheel controls capability, temperature display capability, light gray leather seat inserts, heated seats, security alarm capability, tire pressure alarm capability, electronic convenience group option, sound group II option.
On the other hand, J package can not have the cloth seat option.
As you can see, the J package lets you choose more options but you don't necessarily get them free, the F package limits your choices.
Probably not the best explanation but gives you an idea. I took these differences from a 2009 sales brochure.