Leaves are made to catch light and have openings to allow water and air to come and go. The outer surface of the leaf has a waxy coating called a cuticle which protects the leaf. Veins carry water and nutrients within the leaf. Leaves are the site of the food making process called photosynthesis . This energy rich sugar is the source of food used by most plants.
Photosynthesis supplies food for the plant and oxygen for other forms of life.
A green plant helped make the oxygen you are breathing today.