Living organisms need to "eat" other living or once-living organisms in order to obtain energy to carry out life processes. Note that some organisms don't need to eat other organisms. These are called autotrophs, because they can generate their own chemical energy by converting energy from the sun or other chemicals!

Living things need food for energy. Anything that does work needs energy. Our bodies do work when we move around. Our bodies also need energy to keep us warm and to make us grow bigger. Cars need gasoline for energy to do the work of driving us around. When a hammer hammers in a nail, it uses the energy we give it by pounding the hammer against the nail.

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Life needs energy. Food provides energy. Without energy, life cannot exist.

Living things use energy in some way shape or form, like growing, playing, and learning. At some point, we have used all of the energy available to us, and unless we get more energy (like getting fed), we die. For example, when plants no longer get water, they will turn brown/yellow and shrivel before they die - though if you start to see this, you may be able to feed the plant (not too much though), and it will get better.