Barred is the specific coloring of Plymouth Rock breed. It's a bit of a mouthful, so the Plymouth gets left off. All ____ Rock chickens are Plymouth Rocks. They come in Barred, Black, White, Silver Penciled (look like Primula and Belladonna without the feathered feet and smaller size), Blue, Buff, Partridge (Pear), and probably more colors. All (unless specifically specified for that color variety) should have yellow legs, eye color and body shape (including the "tent" tail) he talked about. The White Rock is specifically crossed with Cornish (
@bgmathteach, the Dark Cornish? or are there other Cornish varieties?) to get the Cornish Cross meat bird that is mostly what you find in the supermarket. They grow super quickly and get processed around 12 weeks. Any being kept as pets HAVE to be put on a specially diet and even then will likely die on their own around 9 months: body simply gives up. The hybrid is usually unable to reproduce so breeders keep lines of Cornish and lines of Rocks going with the cross happening in other pens.
There are other meat bird lines that are more self sustainable (Rangers, and many of the heritage like Breese). Most of the meat bird specific breeds don't lay all that many eggs in a year. Dual purpose breeds lay more eggs and have enough meat on their frames to be worth eating also. Layer breeds are egg laying machines (we know the problems with that).