Denise works with Arnold. While Arnold is a citizen of the United States, he has taken an assignment with the company at its foreign subsidiary in Berlin, Germany. Arnold is considered a parent-national, also known as an expatriate. An expatriate is a citizen of a company's home country working abroad at one of the company's foreign subsidiaries.
Arnold works with Gunther in the Berlin office. Gunther is a citizen of Germany. He's considered a host country national, which is an employee that is a citizen of the country where a company's foreign subsidiary is located.
Adrienna works with Arnold and Gunther in Berlin. She's a citizen of Italy. She's considered a third-country national because she's an employee that is a citizen of one country, working in another country for a company headquartered in a third country.