Crude oil is a complex mixture of hydrocarbon molecules, which are molecules made of long chains or rings of carbon and hydrogen. It's primary use is as a raw material to be processed by refineries into gasoline, diesel fuel, and airplane fuel. Quite a few products are made from crude oil.
In ancient times American Indians used it as medicine, and for thousands of years it was used to coat the bottoms of boats and to coat skins to make them waterproof.
One of the byproducts of refining petroleum is used as a major source of fuel for cement kilns that produce cement that eventually becomes concrete.
Today we use it for what seems like every thing around us:
Asphalt on roads and parking lots
Roofing shingles and roof coatings
Pipe for houses and city water and sewer systems
Ink on newspapers and magazines
Clothing from synthetic fabrics
Computer circuit boards
Styrene which becomes styrofoam (TM)
Hardhats and motorcycle helmets
Cassette tapes, video tapes
Electrical insulation in buildings and computers
Household detergent such as Tide (TM)
Fertilizer used to grow corn and other crops
Adhesive in plywood
Car battery cases, computer battery cases, etc
Refrigerants used in household refrigerators and commercially
Soft contact lenses
Antitfreeze used in auto cooling systems
Insecticides, herbicides, fungicides
Fan belts on engines
Trash bags and grocery bags
Furniture and cabinet coverings such as Formica (TM)
Footballs, basketballs, soccer balls,
Tubing used in medical hospitals for blood, fluids, etc.
Insect repelant and mosquito netting
Adhesive and packing tape
I could go on, as the list is seemingly endless....