You can have the greatest products and services in the world, and if no one knows about them your business will fail. You can have the greatest advertising materials in the world, but if you don't aim them at the right people — those people who will buy — your message will fall flat. You can have the greatest marketing campaign in the world, but if you don't follow up with genuine customer service and good products, your marketing will be nothing but a bunch of noise.
If we use the analogy of a journey, ADVERTISING MEDIA is the vehicle you use to transport your message to the customer. SALES is the driver, the one-on-one contact to bring a human element into the picture to provide direct customer service. MARKETING is the map, the guideline of where you are now and where you want to go. PUBLIC RELATIONS is the flash, the bling, the style with which you journey. You can travel in an old beat-up pickup truck, or you can travel in a shiny Lamborgini. You'll hopefully get there either way, but there will probably be fewer starts and stops, breakdowns, and you'll get more attention if you travel in style.