Crude consists of several types of oil hydrocarbons with different precipitation temperatures. During the fractional distillation process, and at different boiling points this elements will be extracted. The fractions at the bottom have the highest heat, where the most heavy materials are eliminated, such as bitumen used for the asphalt of streets. Then follows the fuel for airplanes and heavy machines, then the Diesel and kerosene (fuel for airplanes). Last but not least come the lightest products, gasoline and gaseous gas. Of course, this materials are still in crude form, that way their process continues in other, special, refineries.
Although not everybody in the Oil Industry joins actively the refining process, it is recommendable to know about this part of their industry branch. This way they will gain more information about which oil it's easier and favourable for the refining process. The two most desired types are the light and sweet oil WTI and Brent Crude.