Erik is quite correct, and yes, this was Steve Jobs' philosophy as it was Henry Ford's (“If I had asked people what they wanted, they would have said faster horses.”)
Most people get the roles of Advertising, Sales, and Marketing, mixed up.
Advertising typically involves broadcasting product or service offerings. Think of TV commercials, billboards, magazine ads etc.
Sales typically involves narrowcasting product or service offerings. Think of your vendor showing up with donuts, or giving a presentation to management, etc.
Marketing on the other hand involves looking at product or service offerings, existing or potential, from the prospective customer's point of view. Marketing helps inform product creation and development as well as sales and advertising. In the graphic arts industry, the marketing function is typically wrapped up into the product engineer's role. In my experience, that's not a particularly good situation.