The euro is the official currency of the 19 countries that make up the Eurozone. As a common currency, it is used in many financial and investment markets, such as stocks, bonds, and foreign exchange. The euro facilitates international investment by providing a single currency that can be used to buy, sell, and trade assets from different countries. It also helps to create a more unified market, which allows for faster, more efficient transactions and investments, making it easier to diversify assets and manage risk. The euro also helps to reduce currency exchange costs for investors who want to buy and sell financial assets in different countries.