Plants are critical to the existence of all living things. Without plants, there would be no food for animals.
In order to produce energy, plants use a tiny structure called a chloroplast to absorb light energy from the sun in a process called photosynthesis. Chloroplasts in plants use a green pigment called chlorophyll to absorb sunlight. Chlorophyll is the reason that plants appear green.
Bacteria living on the roots of plants convert nitrogen in soil into a usable form for living things. Converting nitrogen into its usable form is called nitrogen fixation.
Plants use carbon dioxide during photosynthesis to produce oxygen. The oxygen produced by plants is breathed by people. Without plants to convert carbon dioxide into oxygen, there wouldn't be enough oxygen in the atmosphere to support the needs of living things.