Your pass will only cover the country/ies for which it is booked. Should your route take you out of the country, you will need to buy an extra ticket or ensure you have a pass which covers that country too.
For example: You have a (one country) Italy Pass. On your last day, you’re leaving Italy and going to Germany, where your flight departs. You can either purchase an individual journey to Germany OR purchase a Eurail Global Pass instead.
