What's the difference between "Cage Free," "Farm Fresh," and "Free Range"?

NPR's Anders Kelto has assembled a glossary of terms "for the wannabe informed egg buyer" that contrasts what you might think these phrases mean with what they actually mean. If you've ever wondered what all the jargon on the side of egg cartons means, this article is for you. Here's the entry for "Cage Free":

What You Might Think It Means: Chickens happily wandering around a big red barn, pecking at corn kernels on a hay-covered floor — like the feeding farm I used to visit with my grandma.

What It Actually Means: Exactly what it sounds like: The hens don't live in cages. But they don't live in bucolic red barns, either. They usually live in aviaries: massive industrial barns that house thousands of birds. Each bird has, on average, 1 square foot of space.

Shapiro and other animal welfare advocates believe cage-free birds are better off than their caged counterparts. "They're not exactly living on Old McDonald's farm, but they're able to walk around, perch, lay their eggs in a nest and spread their wings — all important natural behaviors," he says.

But the science around the health of cage-free birds is less clear. Janice Swanson, an animal scientist at Michigan State University, has been leading a three-year study of egg production techniques.

She says cage-free birds have more feathers and stronger bones and exhibit more natural behaviors. But crowded aviaries also come with risks: reduced air quality, and twice the likelihood of dying. Over the course of their three-year study, less than 5 percent of birds in cages died, compared with more than 11 percent of cage-free birds. One of the most common causes of death was pecking by other chickens.