Cannabinoids, as well as their cousins terpenes, are simply the chemicals that provide actual relief to patients by inserting themselves into special receptors in the tissues and cells of the human body. They are among more than 480 natural components found within the cannabis plant.
These special receptors are part of what is known as the endocannabinoid system. This mechanism, which helps modulate many bodily functions--including appetite, sleep, anxiety level, and cognition--is intimately tied to the nervous system and immune system. In fact, particular cannabinoids target specific types of receptors located on the surface of cells in different areas of the body.
This targeting is formally called a binding affinity. Some molecules may feature a relatively low binding affinity that offers poor or moderate efficacy for a patient, while other pairings feature a very strong affinity that, when combined with cannabinoids from high-quality plants, can result in superb medical benefit or psychoactive effects.
The last post is a picture of 5 terpenes and their effects on cannabis: "The aromas are given off by terpenes, volatile aromatic organic hydrocarbons that are produced by plants and even some insects; in cannabis, terpenes are the precursors for not only odors, but vitamins, pigments, resins, essential oils, cannabinoids and other elements found within the plant as well."
A-pinene: anti inflammatory, bronchodilator, aids memory, anti bacterial--also found in pine needles.
Linalool: anesthetic, anti convulsant, analgesic, anti anxiety--also found in lavender.
Beta caryophyllene: anti inflammatory, analgesic, protects cells lining digestive tract--also found in black pepper.
Myrcene: contributes to sedative effects of strong indicas, sleep aid, muscle relaxant--also found in hops.
Limonene: treats acid reflux, anti anxiety, anti depressant--also found in citrus.
Sources: massroots.com; and montereybayaltmed.com.