Whole grain is the broad category for any cereal grain that still includes the entire kernel — bran, germ, and endosperm — in their original proportions. Whole wheat is one specific whole grain: products labeled whole wheat use the whole wheat kernel.
So all whole wheat is whole grain, but not all whole grain is whole wheat. Oats, brown rice, barley, rye, quinoa, and other intact grains also count as whole grains. For packaged foods, look for “100% whole wheat” or “100% whole grain” on the label rather than vague terms like “wheat” or “multigrain,” which may still include refined flour.
Source: Oldways Whole Grains Council — What’s a Whole Grain? A Refined Grain?