Tea and coffee are familiar infusions: plant parts (leaves and beans) steeped in liquid (water), impart aroma, color, and flavor before being removed.
Petals, herbs, and leaves can be similarly infused into water or oil, then used for soap making or in other bath and body goods like salves and balms, imparting fragrance (and other skin-loving benefits).
A decoction is similar to an infusion. Tough plant parts (like stems and bark) are steeped in liquid just like infusions, but for longer periods of time, usually at higher temperatures, producing a more concentrated end product.
The highest quality essential oils are 100% pure. These aromatic plant extracts are made entirely by nature. If you've ever felt uplifted by a forest walk among pines; while mincing fragrant herbs for a meal; or after inhaling a sweetly floral bouquet; you've experienced the aromatherapeutic qualities of natural essential oils for yourself.
To produce essential oils, steam, water, or pressure are used to distill or express a plant's "essence" -- a concentrated, often deliciously scented, oil -- from its leaves, flowers, stems, roots, and/or bark. Huge amounts of organic material render a small amount of essential oil; in the case of rose oil, for example, it takes 1.5 million (4 tons of) rose blossoms to make just 2 pounds of rose essential oil.
Distillation is a tedious process requiring time, space, and elaborate equipment, and it takes enormous yields of plant matter to extract very little essential oil, so these concentrated oils are a more expensive scent option than synthetic fragrances. They're also one of the pure, natural ingredients that distinguish hand made artisanal soaps from mass produced, lab-created bars.
Delicate plants (like jasmine, tuberose, lily, and gardenia, among others) don't tolerate steam distillation well, or don't release their essences readily under pressure. For these plants, essential oils are extracted using chemical solvents which are removed from the final product before it goes to market. The fragrant liquid that results is called an absolute to differentiate it from an essential oil, both because of the extraction method used, and because it's significantly more concentrated.
Also known as "flower waters," hydrosols are produced by steaming fresh plant parts like petals and leaves, then collecting the aromatic condensation that results. Although similar to their essential oil counterparts, these fragrant waters contain both fragrant essential oil particles and the water used to distill them, so they are less intense and concentrated than essential oils, and typically offer "greener" scent notes.
Fragrances are scents developed by chemists that do not occur naturally. Fragrance oils are man-made aromas containing some, or all, synthetic ingredients. Natural fragrances mix scented natural isolates and raw materials (like resins) with essential oils to create an aroma. Often diluted, fragrances may contain up to 95% petrochemicals. Much less expensive to produce than essential oils (and their related absolutes and hydrosols), fragrances are neither naturally occurring, nor do they offer the pure aromatic notes that earth-grown essential oils do.
Vegetable oils (like coconut, olive, and almond) and butters (like cocoa, mango, and shea) have unique scents of their own. Their subtle, natural plant aromas emerge from whatever is made with these ingredients. Other scent-bringing ingredients include: petals, flower buds, beeswax, honey, oatmeal, herbs & spices, yogurt, teas & coffee, cocoa, seaweed, salt, and many more. The naturally aromatic possibilities are infinite, even with "unscented" product formulations.