French is the main and most common language spoken in Paris. However since Paris is an international city, you can also hear many other languages, including English, Arabic, Spanish and Chinese. I often hear different languages while riding public transportation or walking through neighborhoods. It's one of the things that make Paris such a culturally diverse place.
France uses the euro (€), which is also used by many other European countries. Euros come in both coins and paper bills. Since I'm used to paying with U.S. dollars, living in France has helped me become more comfortable using another currency and comparing prices.
One interesting thing about using euros is that I now have to think about how much something would cost back home before deciding whether it's a good deal. At first, I would constantly convert prices into U.S. dollars in my head, but after living here for a while, I've started getting a better sense of what things should cost in euros.
Another thing I've noticed is how convenient it is to travel between countries that use the same currency. Instead of exchanging money every time I cross a border, I can continue using euros in many parts of Europe. It's a small convenience that makes traveling and budgeting much easier, especially as a student studying abroad.