The energy sector is that part of the economy that produces, refines and supplies the natural resources that the world uses to keep things moving. This is a really long way of saying oil. The largest company in the world dominates this sector, ExxonMobil, which has 17% of the market capitalization of the energy sector worldwide. Next four different countries offer up each of these with roughly the same 5% shares: BP, Chevron, Total ELF, Royal Dutch Shell.
The energy sector came into its own when the value of a barrel of gas went fivefold in five years until 2008 but since has shrunk some. Usually looked as a source for steady dividends and solid earnings, oil producers, wildcats, tankers, refiners and everyone in between hit it big during this time. Things have settled down for now but count on continued earnings and payouts as demand for black gold remains tight.