Final answer:
U.S. travelers to Europe check the currency exchange rate, which is the value of one currency for the purpose of conversion to another currency.
Step-by-step explanation:
When people from the United States travel to countries in Europe, they are checking the currency exchange rate. The exchange rate is the price of one currency expressed in terms of units of another currency. It enables travelers to determine how much of the foreign currency they can obtain with their U.S. dollars and is crucial when comparing GDP across countries with different currencies.