Did you buy something today? A hamburger and fries for lunch? The latest CD? Whatever you bought probably would have cost more without competition. Competition is one of the pillars of free enterprise. It benefits you(the buyer) and the seller:
In a competition market, producer constantly strive to reduce their production costs to increase profits. The increased efficiency that allows them to reduce their costs also lets producers sell their goods at a lower price. Thus, by promoting efficiency, competition leads to lower prices.