In fact, sales is an essential part of marketing, but it's not and never can be a replacement for the full marketing process. Selling is one of the ways you communicate your marketing message. It's the point at which you offer the product, you make the case, the customer makes a purchasing decision, and the business-to-customer exchange takes place.
Without all the marketing steps that precede the sale — fitting the product to the market in terms of features, price, packaging, and distribution (or availability), and developing awareness and interest through advertising, publicity, and promotions — even the best sales effort stands only a fraction of a chance for success.