They are money because people accept them as money. For this to happen, money must do three things. First, money must serve as a medium of exchange: you pay tuition; you receive an education in exchange. The alternative is bartering, but that is complicated and inefficient. Second, money must serve as a store of value.
What is the current state of financial integration in Europe? The current degree of financial integration in Europe varies between market segments. A simple, but useful quantitative measure of financial integration is to check the validity of the law of one price. It states that in a fully integrated market risk-adjusted prices should be equal irrespective of the place of transaction.