Natural Gas is a fossil fuel formed from plants and animals buried underground and exposed to extreme heat and pressure. Natural gas is used domestically for cooking, as a power source, in agriculture, and in industrial manufacturing. Natural gas prices fluctuate constantly depending mainly on production issues, stockpiles, weather conditions, economic growth, crude oil prices, and more recently coal. Natural gas is commonly measured in MMBtu, with 1 MMBTu equaling 1 million BTU (British Thermal Units).