Coal

• Coal is one of most affordable fossil fuels.Thomas Northcut/Photodisc/Getty Images
  
  Coal is formed by decayed land vegetation over millions of years. It is a solid fossil fuel, and when its layers are compacted and heated, the deposits turn into coal. Usually extracted in mines, this fossil fuel is mostly used to generate energy. There are several types of coal such as lignite, sub-bituminous, bituminous and anthracite. Many countries such as China use coal for energy because it's more affordable than oil or natural gas.
  
  

Oil

• Oil can be found by drilling.Jupiterimages/Photos.com/Getty Images
  
  Formed from the remains of marine microorganisms, oil gets trapped between rock and sediment. This liquid fossil fuel can be extracted by drilling and is the most widely used. Vehicles and other forms of public transportation uses it for gasoline; buildings and homes use it for heat; and it supplies energy resources. It consists of organic compounds that are transformed during the refining process.
  
  

Natural Gas

• Natural gas has many uses such as to cook or to heat your home.David De Lossy/Photodisc/Getty Images
  
  Cleaner than coal and oil, natural gas is formed from the remains of marine microorganisms. Even though it is widely used, especially in developing countries, there is fear it may run out. Natural gas is mainly made up of methane, which is compressed in small amounts deep into the Earth. Highly flammable, it is used mostly for cooking and heating. Reserves are evenly distributed around the globe, and it can be retrieved by drilling.
  
  

Other Resources

• Besides fossil fuels, there are renewable resources we can use .The Department of Energy and many private companies are working to develop these technologies.