Who are your customers? Your customers are people who buy, but they can also be those who simply benefit from your efforts. These customers may be paying customers or internal co-workers. Everyone who works has customers.
Without external customers there would be no sales, no business and no works.
Without internal customers there would be no product or service to sell. Internal customers require the same attention that external customers demand. It is easy for internal individuals or groups who are totally isolated from the external customers to forget how their work affects the external customer. However, all interactions eventually influence the external customer.