Eating is taking in food to get energy or nutrients or for enjoyment. People and animals need to eat because they cannot make their own food inside their bodies like plants. All plants' energy comes from the Sun. Plants take the Sun's energy, and they are eaten as food. The animals then eat each other for their energy.
When a plant collects energy from the Sun through its leaves, it is called photosynthesis.
Too much food make people fat. Too little makes then thin.