Gasoline is the automotive fuel most cars on the road today are using. It is one of the many things that can be extracted from crude oil, which has everything from parrafin wax to natural gas in it. Diesel fuel is one of the materials found in it as well. All of these are called hydrocarbons, which are elements made from hydrogen and carbon. Gasoline is also referred to as gas, petrol, petrolium, and fuel (a universal term which isn't only gasoline).
Gas prices shift due to a large number of factors, including extraction costs, trade agreements, supply/demand, speculation, taxation, and more. Cost of alternative fuels don't play much of a factor at the moment, because such a small percentage of the world's cars can use alternative fuels.
The chemical make-up of octane is C8H18, which is eight carbon atoms for every 18 hydrogen atoms, per molecule. If this was strictly what came out of a gas pump, it would be considered 100 grade octane.Typical gasoline consists of hydrocarbons with between four and 12 carbon atoms per molecule (commonly referred to as C4-C12).