Refining is the process of creating fuels for internal combustion engines from mineral hydrocarbons extracted from under the earth. It is a highly lucrative business, as most of the world's economy relies on these fossil fuels for energy. Some of the richest corporations in the world have been formed in the oil business, and indeed the industry could never have grown so large without the large-scale industrial organization that corporations have provided.
Refining takes place in a cracker, which produces various grades of fuel from the oil.