All matter is composed of such substances. Matter can not be created nor destroyed but may change its form, such as occurs in a chemical process. Chemical process can occur within living organisms or from nonliving sources. In the early 1700s, it was believed that chemical synthesis could occur only in living organisms and organic compounds were defined as coming from living organisms, whereas inorganic compounds come from nonliving sources. However, today, we know that chemical synthesis can occur outside of living organisms.
Organic compounds are the compounds made up of the chemical element carbon.
Inorganic compounds do not contain carbon. Inorganic chemicals include sulfur, oxygen, nitrogen, silver, copper, etc. Living things are composed primarily of organic compounds but the organic compounds also have lots of hydrogen and oxygen with small amounts of other inorganic elements sulfur, copper, magnesium, etc. When living things die, these organic compounds may change form to become compost, or with even greater time, petroleum. All things originating from living things are organic but anything containing carbon is also organic.