honestly pasture raised and you know the farmer really raises the chickens well is the only kind that means a thing. free range, organic, natural, all mean absolutely nothing. The only thing that means something is talking to the farmer about how he or she raises their chickens.
Free range means they have to have access to the outdoors a small portion of the day. It doesn't mean they have to actually go outdoors, or have adequate outdoorspace, or bugs and weeds in said outdoor space to eat. It doesn't mean the chickens can't be overcrowded the rest of the time inside.
Organic means their feed is organic. Which I suppose means it's GMO free which technically means something, but they are still kept in filthy, inhumane, insanitary conditions, and lack the sunlight and bugs and weeds and such that make for healthy chickens.
Naturally raised means nothing really. Chickens can't be given hormones anyways. I guess if they are antibiotic free thats good, but again, terrible living conditions lacking the things that make them healthy, it really means nothing.