Wheatgrass essentially IS wheat (wheat greens, that is). However, it contains no wheat gluten if that's what you're afraid of. You can probably eat it even if you have a wheat allergy.
The best way to get wheatgrass is to grow it! If you do not want to grow it you can buy it at a healthfood store or some supermarkets. If you live in the greater Cincinnati area you can get it...
Yes, it is a type of grass that has been genetically altered to produce larger seeds than its ancestors to be able to be crushed into flour to make bread, as an example.