This wording confused me at first. I thought, “layers of chicken?!” To clarify, the book separates chickens into “light” and “heavy” breeds, which literally refers to their typical weight. Heavy breeds are bred for meat, and are intended to be “table birds.” Light breeds are not bred specifically for meat, and are typically “layers” of eggs. The book does list some crossovers, however–”heavy” birds that are also decent layers.