A fuel pump is a device used to transfer gasoline or diesel from a vehicle's fuel tank into its engine. It works by using an electric motor to create suction, which draws fuel through a filter and then forces it through pipes and into the engine. The purpose of the fuel pump is to ensure that there is enough pressure in the system for the fuel to reach the engine and be burned, providing power to move the vehicle. Without a functioning fuel pump, the car won't start or run properly.