Fragrance oil(s), also known as aroma oils, aromatic oils, and flavor oils, are blended synthetic aroma compounds or natural essential oils that are diluted with a carrier like propylene glycol, vegetable oil, or mineral oil.
To allergic or otherwise sensitive people, synthetic fragrance oils are often less desirable than plant-derived essential oils as components of perfume. However, synthetic versions of the same compound as a natural essential oil are usually very comparable. Furthermore, natural oils are in many cases significantly more expensive than their synthetic equivalents.
Aromatic oils are used in perfumery, cosmetics, flavoring of food.
Some include (out of a very diverse range):
References
Fragrance oil Wikipedia(Text) CC BY-SA