Magnesium is an essential mineral that helps muscle and nerve function and keeps the heart rhythm steady and bones strong, and is found in foods like green vegetables, nuts, cereal, and yogurt. The document discusses the importance of magnesium for health, food sources of magnesium including many green vegetables and nuts, and dietary recommendations for magnesium intake. It also notes that magnesium may help prevent illness and that those with diabetes should take additional magnesium.