why do chickens on the farm look nothing like a foster farm chicken in the super market?

The ones on the farm are still walking about with all of their parts, not in a freezer at the supermarket.

Aside from the fact that they're not walking around, and have been plucked naked ??

It all depends on the breed... White Leghorns are one of the primary breeds used by Foster Farms, and are MEAT birds bred for "intensive farming" systems.

Our "farm chickens" vary in size by the breed / purpose... we have meat birds that are fat and stocky, multi-use birds that are leaner, and "decorative" birds that are pretty skinny but have lovely plumage.

Their feathers and head are gone, other than that they look exactly the same.