A grain and a seed are different parts of the plant. They have much different nutrition and digestibility. The grain is the edible "fruit” of the plant, usually found at the top of a stalk, and very often called a “seed” on the internet. It has a moderate amount of nutrition and digestibility for some animals, and provides most of the cereals eaten by people all over the world.
The seed, on the other hand, contains all the nutrients required to build a new plant. These nutrients are dormant and protected within a hard shell until the seed is germinated or sprouted. Then it activates(enzymatically speaking) and becomes extremely digestible and a super-food supplier of nutrition.
For example, barley is a cereal grain when harvested for its fruit (the grain we grind into flour), but its seed contains no gluten because the protein is significantly reduced in the enzymatic process during sprouting. The protein containing the gluten will increase later in the mature plant’s fruit. Both wheat grass and barley grass are considered gluten-free until they begin to produce fruit.
The U.S. Food and Drug Administration, in its finalized gluten-free label rules, has said that wheat grass and barley grass could be used to make foods labeled gluten-free, as long as the finished products contain less than 20 parts per million of gluten (which can get mixed in during processing of the rest of the plant), as is the case with Heirloom Barley sprouted barley seed powder.
This makes it very suitable for people looking to avoid grains due to gluten sensitivity, but needing plant-based enzymes, vitamins, and minerals. Many gluten-sensitive people find they can enjoy Heirloom Barley. Sprouting makes a world of difference.