If you buy both fragrance oils and essential oils, be careful not to mix them up. They are quite different, and used for different purposes.
Essential oils are so called because they are the essence of the plant or other resource from which they are extracted. The essential oil gives the plant its distinctive fragrance.
Fragrance oils may or may not contain essential oil. They are usually made using chemicals to reproduce the smell of particular flowers, and used in perfume and similar products. They do not have any medicinal value, and in fact, they may contain dangerous chemicals that could cause damage to skin or other organs. Even if this is not the case, they are still not beneficial for use in aromatherapy.
Genuine essential oils are a completely natural product. They are usually pleasantly scented, but not always. However, the ones that don’t smell that good are rarely used, for just this reason.
Essential oils contain the healing essence, or at least that part which is oil-soluble. The part which is water soluble is often available in the form of a hydrosol or flower water.
There are several different methods which can be used to extract the essential oil, but most are prepared using either steam distillation (which also produces a hydrosol as a by-product) or cold pressing the peel (mainly citrus fruit).
Absolutes are expensive, so they are also often sold in dilute form, which are less heavily fragranced and easier to use, as well as being cheaper.
Finally, there is a new process called CO2 extraction which produces two different oils, depending on the amount of pressure used. These are select and total extractions. The select type is closest to a regular essential oil.
The medicinal uses of essential oils are due to their chemical composition, much more than their scent. There may well also be some emotional benefit from using oils with a fragrance which you enjoy, but this is not the whole story.
Don’t choose essential oils purely by their fragrance, in particular when blending, but pay attention to their known therapeutic effects. There’s little point, for example, in making a blend that contains oils that have opposite effects.
Enjoy your fragrance oils and your essential oils, but keep them for their intended purposes.
I offer a wide range of essential oils in my online shop.