Pastured eggs come from pastured chickens. While "pastured" can be used to describe any animal raised for meat or eggs, "pastured" is most often used to describe poultry and eggs from chickens that have been raised the way you imagine a chicken would want to live: they walk around in open fields and woods, they hunt and peck for food, and they go back into a hen house at night to roost, nest, and lay eggs. Without forced molting and lights, pastured eggs are also seasonal, you'll see more available in the spring and summer, with supplies dipping low into fall and through winter.
Pastured, for the most part, means the animal was allowed to live on a pasture for most of its life. In the case of chickens, "pasture" could mean a pasture, a meadow, fallow fields, or even woods.
The result in eggs is tremendous; they have deep yellow, even orange yolks from their greens-rich and varied diet, and the whites are clear and bouncy.
Do Pastured Chickens Just Eat Grass?
The simple answer is no, but that's because, unlike grass-fed cows, chickens don't naturally want to just eat grass. Pastured chickens are allowed to hunt and peck for food as chickens are want to do. They don't eat grass, despite how it looks when a chicken hits a meadow, but primarily look for seeds and insects. They'll also eat the occasional small rodent or reptile thrown in if they can catch them!
Pastured chickens often receive a supplemental feed in the winter or during dry months. This feed may or may not be certified organic (if the eggs are also labeled "organic" then the feed would need to be certified as such).
Are Pastured Eggs Organic?
Sometimes they are and sometimes they're not; it's a separate issue. Eggs can be organics but not pastured, and they can be pastured but not certified organics. Since they aren't crowded together in unhealthy conditions, pastured chickens don't tend to receive unnecessary antibiotics or hormones. If the eggs are labeled organic, they won't come from chickens who were treated with either.
What Does Pastured Mean?
"Pastured" doesn't have a legal meaning or certification process. There are people, to be sure, who slap a "pastured" label on their eggs even though the chickens really just have an outdoor run alongside the chicken coop. Sure, the chickens are better off than in a factory farming situation, but they aren't running on a pasture either.
Overall, pastured animals tend to be raised on small farms and the farmers often sell at farmers markets and other direct-to-consumer methods or through co-ops. It is usually easy to find out more about a specific farm that sells pastured meat or eggs since they are often rightfully proud of how they care for their animals.