Wellness can be defined as more than just your health and actually has to do with your overall state. Mental health, physical health, environmental health, financial health, etc, all come together to make up your wellness.
If you care about your health, you already care about part of your wellness. Physical activity and diet aren’t all there is to living a healthy lifestyle. Things like minimizing stress, having solid support systems in your life, saving money etc. are parts of it too, and are just as important as working out or, eating healthier.