Retail businesses buy merchandise from a variety of wholesalers and sell it directly to consumers. Supermarkets, mail order catalog merchants, computer stores, dress shops, department stores and convenience marts are retailers. Wholesalers buy merchandise from manufacturers or brokers and resell the goods to retailers. People with a particular skill sell it to consumers or to other businesses, depending on the skill. Manufacturers assemble components or process raw materials into products usable by consumers or other businesses.
Developers create and finish a saleable commodity by assembling resources for a one-time project.
One way to determine what is useful for your customers is to identify and describe the problem that your business will solve. For example, a window washing service solves the customer's twin problems of wanting clean windows but lacking either the time or physical ability to clean windows himself. If you accurately understand your customers' problems and needs, your business will have a better chance of success. Also, I'd like to be able to specify the exact ingredients I want in my meal. And, it would be really swell to have a glass of wine or beer with the meal.