essential oil; volatile oil
Commonly used in aromatherapy, cosmetics, and natural products. Refers to concentrated plant extracts.
I put lavender essential oil into the aroma diffuser.
refined oil
A broader term for any oil that has been purified or processed. Less common than the essential oil sense.
This factory produces refined oil from crude oil.
oil refinery
Compound of 精 (refine, pure) and 油 (oil). The term is used both for essential oils (plant extracts) and refined oils (processed petroleum or other oils).