Oil pumps are one major component in a total oil control system. If you can't pump enough oil to the top of the motor and throughout it, your engine is done. Most traditional V8 oil pumps are driven off of the distributor oil pump drive rod. Oil pumps sit down in the oil pan with an oil pump pickup tube that is usually in the lowest part of the oil pan where the oil can pool and collect.
Oil pumps are made in many configurations from low volume race pumps, everyday use and high volume. Generally the more oil you pump through your engine, the more power that your oil pump robs your engine of. Moving oil through a pump does take power to do. The give and take here is to get a pump that pumps plenty of oil for your application. Too much oil and you lose some horsepower. Too little and you have NO horsepower! Low volume oil pumps are generally used for drag racing applications where the race is very quick. Oil is better than it used to be and can withstand more than in past years. There are a lot of everyday replacement oil pumps. Those are great for daily drivers and non-race use. High volume pumps are a general group of oil pumps made for higher horsepower applications where the engine is run longer such as on a muscle car or other high performance street car, or a circle track race car. They pump enough oil to keep a high performance engine well lubricated.