What is the difference between firms in business marketing and advertising and promotion to the customer? It is part of a problem in my studies of the company and level of due diligence, but I'm not sure what each of them are, please help. Thakyou (:. I think I found a solution to business promotion business is helping sales of 1 products companies to other companies or companies that then resell them, use them as elements of services or products they offer. Or used for backup of their duties. Customer marketing and advertising is the immediate sale of the buyer. Best of luck to you personally with the scientific evidence.