Like when you squeeze lemon juice over a cut apple to keep it from turning brown, that is an antioxidant. Fruits and vegetables contain many compounds, which are antioxidants. These molecules bind with "free radicals," which are extra oxygen molecules floating around your blood stream. These free radicals are thought to damage cells, damage their DNA, accelerate aging, are responsible for brown age spots and wrinkles. Populations that eat more fresh fruits and vegetables generally have lower rates of heart disease, stroke, cancer, and diabetes. So eat your fruits and veggies!