From Investopedia:

The energy sector is comprised of companies focused on the exploration, production, and marketing of oil, gas, and renewable resources around the world. Popular energy sector stocks include upstream companies that are primarily engaged in the exploration of oil or gas reserves. Well-known companies in the sector are Occidental Petroleum Corp. (OXY) and Diamondback Energy Inc. (FANG). Downstream companies include Marathon Petroleum Corp. (MPC), which refines and processes oil and gas products for delivery to consumers.

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