The pump is run by a belt off the car engine, and requires power steering fluid or automatic transmission fluid, stored in a tank either mounted to the pump or nearby it, to operate the most efficiently.
The pump works by using the fluid to create high pressure, which is then used to reduce the force you apply when turning your steering wheel; if you don’t have this reduction, then you eventually develop Forearms of Steel. Some cars have variable-assist power steering systems that supply more help at slower speeds and less help at higher speeds.
The best thing about this type of steering system is that it can reduce over-correction accidents on the highway at higher speeds; some drivers also like the feel this type of setup provides at those higher speeds.
Just like any other part of your car, the power steering pump needs a little care and maintenance. First, check your power steering fluid level when you change your oil. It is a good idea to do this when the engine is warm.
The tank is usually clearly labeled “Power Steering Fluid”. Power steering fluid is not “used up” like gasoline, so if your car is low chances are there is a leak in one of the hoses or around a seal.
If all the fluid is drained, then there is no high pressure created, so your easy steering goes away, and the pump will quickly burn up.
Also, while you are checking the fluids, make sure the belt is tight and in good condition. Second, try not to hold the steering wheel as far as it will go in either direction as this puts undue strain on the pump and can cause damage.
Third, keep your ears open for any high pitched squealing coming from the pump drive belt.