Essential oils, also known as ethereal oils, are volatile, aromatic compounds derived from plants. Found in only about 10% of the plant kingdom, these oils are present in secretory structures such as glands, ducts, cavities, and hairs. Chemically, they belong to categories such as terpenes, phenols, and nitrogen-bearing compounds, consisting of carbon, hydrogen, and other elements like oxygen, nitrogen, and sulfur.
Source:
phys.org