Essential oils are natural aromatic compounds which are found in the flowers, stems, roots, bark and other parts of plants. From these plants, the essential oils are extracted by a steam distillation process. The particular mix of chemical constituents are what give plants their distinctive smells, offering up their delicious and unique aromas. Practically speaking, these oils provide plants protection against predators and disease.
Unlike vegetable oils, Essential oils are not "oily" - they are not made up of fatty lipids or acids found in vegetable and animal oils. They are light, fat-soluble, but not water-soluble (as anyone can attest to if they've tried to blend essential oils with water). Pure essential oils vary in color, viscosity and taste.