Final answer:
External customers are those who buy or lease an organization's offerings; other parties affected by these exchanges are subjected to externalities. In foreign exchange markets, firms involved in international trade are typical demanders and suppliers of currency, navigating exchange rates that could impact various stakeholders.
Step-by-step explanation:
External customers are individuals or entities that are not directly connected to an organization, but who seek out, research, and ultimately purchase or acquire the products or services that the organization offers. As an example, a concert producer who is planning to build an outdoor arena for country music concerts becomes the supplier, whereas the concert attendees who buy tickets are the external customers. However, those living nearby who are affected by the noise are neither customers nor suppliers but are impacted by the externality or spillover effect of this economic activity.
Firms engaging in the foreign exchange markets to support their international trade activities represent demanders and suppliers of currency as they need to exchange their home currency for foreign currency and vice versa. These transactions also have potential externalities, such as fluctuations in exchange rates that may influence different stakeholders - from exporters and importers to travelers and foreign investors.