It typically covers three categories of workers.
- US hires or "expats": These are citizens or legal residents of the United States who have been hired to work outside of the United States.
- Third country nationals (TCNs): These are workers hired in a country outside the United States who are assigned to work in a country other than their country of origin. An example is a French citizen who is assigned to work in the United Kingdom.
- Local nationals: These are workers hired in a country outside the United States to work in that country. For example, a French citizen assigned to work in France is a local national.