Internal communication occurs within a company between supervisors, subordinates, and colleagues, and can flow downward from supervisors to staff, upward from staff to supervisors, or horizontally between colleagues. External communication happens outside the company between staff, customers, suppliers, and the public, such as a salesperson interacting with customers, distributing brochures, or a manager promoting products through advertisements. Effective communication, whether internal or external, is important for businesses to get work done, tell others about their products and services, and discuss new ideas.