Fossil fuels like diesel and petrol are the products of natural oil which are refined for a product of chemical consumption, efficient for combustion engines.
Fossil fuels are diesel, petrol, natural gas. Biofuels have been around for longer than cars, but cheap gasoline and diesel have kept them on the fringe for long.
Reason why we are looking for new kind of fuels for cars are climate change, increase of the price for fossil fuels, less fossil fuels, pollutions and emissions from fossil fuels.