I believe  pasture-raised is signifying that the chickens are living in a field eating insects and such from the ground.

Free range just means they don't live in cages. 

Many US free range large farming corps put them in a large enclosure on the dirt and still feed them the same grain and such that they would get in the cages. 

 Thanks, I read up on it a bit. It seems they can get away with access to dirt through a small hole in the barn, so many chickens may never actually make it out of the barn. Meanwhile, these guys seem like the real deal. https://www.youtube.com/watch?v=NjQMdjsZG1U 

 I have a friend who designed self-moving pens. They are solar powered and slowly roll across the pasture. 

Protects his birds but they still get their nutrition.