If you see this on a label on food, it means that the food item has no gluten (a type of protein), and has no grain (wheat) in it. Some people are severely allergic to these, so it's important to know for some.

Gluten is a general name for the protein found in wheat (durum,emmer,spelt,farina,farro, KAMUT khorasan wheat and einkorn). rye, barley and triticale. Gluten helps food maintain their shape, acting as a glue that holds food together. Gluten can be found in many types of foods, even ones that would not be expected. While grain free is the elemination of all grains including wheat, rice, corn, millet, barley and oats. A grain free diet has been proven through the personal experience of hundreds of people worldwide who have experienced significant relief from symptoms of chrohn's disease (and many other illness of the digestive system)