It's chemical energy.
It started out as energy carried in solar radiation. It was absorbed by plants, and they stored it as chemical energy in their stems and leaves. The plants got cut down, washed off, and delivered to the supermarket. Your mom brought them home, camouflaged them so they wouldn't look like veggies, and put them on your plate while you weren't looking. Eventually, some of them got into your body, got digested, and their energy got stored in your cells as glucose and fat. When you needed some energy to do something physical or mental, you grabbed some of that energy that you had stored as chemical energy, and used it to operate your muscles and your brain. You used the glucose (blood sugar) first, and if you ever reached the point where that was running low, you started to use the fat that you have stored around in many places.
