What are they?
Hydrocarbons are a diverse group of organic compounds made up of hydrogen and carbon atoms. Hydrocarbons are formed from very old degraded algae, plants and other biological matter. Hydrocarbons can be gases, liquids and solids, and are generally used as a combustible fuel source.
Crude oil is a complex mixture of hydrocarbons and other constituents (like metals) that can be processed to produce various fuels, solvents, and polymers (or plastics), among other products.