According to Wikipedia,

an essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile oils, ethereal oils, or aetherolea, or simply as the “oil of” the plant from which they were extracted, such as oil of clove. An oil is “essential” in the sense that it carries a distinctive scent, or essence, of the plant. Essential oils do not form a distinctive category for any medical, pharmacological, or culinary purpose.

http://en.wikipedia.org/wiki/Essential_oil

Essential oils are powerful anti-oxidant concentrates that come from plant material such as flowers, leaves, wood, bark, roots, seeds, and peels. Plant ingredients are put into a distiller and placed over water. As the water is heated, the steam penetrates the plant material and vaporizes the volatile compounds. The vapors then travel through a coil and condense back to a liquid which is collected in a receiving vessel.

A lavender by any other name—and it has a few !

Alhucema, Common Lavender, English Lavender, French Lavender, Garden Lavender, Huile Essentielle de Lavande, Lavanda, Lavande, Lavande à Feuilles Étroites, Lavande Anglaise, Lavande Commune, Lavande des Alpes, Lavande du Jardin, Lavande Espagnole, Lavande Fine, Lavande Française, Lavande Officinale, Lavande Vraie, Lavandula, Lavandula angustifolia, Lavandula dentate, Lavandula latifolia, Lavandula officinalis, Lavandula pubescens, Lavandula spica, Lavandula stoechas, Lavandula vera, Lavender Essential Oil, Ostokhoddous, Spanish Lavender, Spike Lavender, True Lavender.