We can compare the business to a bottle that is left outside on a rainy day and raindrops would symbolize customers. The bottle, alone, would normally catch raindrops without exerting any effort on it. Though, we could speed up the process by using a funnel so we could catch more drops.
Same thing applies to business. Marketing strategies would serve as our funnel to drive more customers towards the business. These customers would later convert into revenues for the business. Most marketing strategies are based on a basic marketing concept -- AIDA.