Essential oils are basically plant extracts, made by steaming or pressing various parts of a plant (flowers, bark, leaves or fruit) to capture the compounds that produce fragrance. It can take several pounds of a plant to produce a single bottle of essential oil. In addition to creating scent, essential oils perform other functions in plants, too. 

Aromatherapy is the practice of using essential oils for therapeutic benefit

Aromatherapy has been used for centuries. When inhaled, the scent molecules in essential oils travel from the olfactory nerves directly to the brain and especially impact the amygdala, the emotional center of the brain.Essential oils can also be absorbed by the skin. 

The applications of essential oils are diverse. Widely used in cosmetics and perfumes, they also have medicinal applications due to their therapeutic properties as well as agro-alimentary uses because of their antimicrobial and antioxidant effects.