The energy industry is the totality of all of the industries involved in the production and sale of energy, including fuel extraction, manufacturing, refining and distribution. Modern society consumes large amounts of fuel, and the energy industry is a crucial part of the infrastructure and maintenance of society in almost all countries.
In particular, the energy industry comprises:

the petroleum industry, including oil companies, petroleum refiners, fuel transport and end-user sales at gas stations
the gas industry, including natural gas extraction, and coal gas manufacture, as well as distribution and sales
the electrical power industry, including electricity generation, electric power distribution and sales
the coal industry
the nuclear power industry
the renewable energy industry, comprising alternative energy and sustainable energy companies, including those involved in hydroelectric power, wind power, and solar power generation, and the manufacture, distribution and sale of alternative fuels
traditional energy industry based on the collection and distribution of firewood, the use of which, for cooking and heating, is particularly common in poorer countries