Power steering reduces the amount of effort that a driver needs to exert when steering.
Hydraulic Power Steering. A power steering pump, which is commonly driven by a belt on the engine, provides fluid pressure to ease the force required by the operator to turn the steering wheel. It is necessary to periodically check the power steering pump reservoir fluid level. If there is a howling sound when turning the steering wheel the power steering fluid is most likely low.
Electric Power Steering (EPS). Some power steering systems are not mechanically belt driven. EPS is becoming more popular. EPS systems allow the driver to have power steering even if the vehicle stalls or is shut down intentionally at stops. Using an EPS system increases fuel efficiency by 1-3% by reducing weight and mechanical losses. Being electrical, it also has built-in self diagnosis features.