I group these all together because for a base fare of 75€, you can purchase a pass and have unlimited access for a whole month to all three. I know it may seem like a lot of money but the cost of a one-way Metro and bus ticket is 1.90€ alone, so if you make at least 19 round trips a month, the pass is the way to go. There are Metro, bus and Velib stations all over Paris, which pretty much guarantees that you will always be in close proximity to one for quick access. For example, within seven minutes walking distance from my studio, I have three Metro stops, several bus stops and three Velib stations! A large number of public transportation options really does put the whole city at your fingertips.
Velib is a rent a bicycle-type service with stations located all over Paris, so you can rent a bicycle from a station near you and drop it off at a station close to your destination. If you do not want to purchase a metro pass, a whole year of unlimited access to Velib is only 30 euros! Something fun about Velib is that it offers two types of bicycles available to rent, the normal kind that you have to pedal and electric bicycles that make going uphill much easier and riding on flat terrain an absolute breeze!
While having a car is a practical necessity in many cities in the U.S. since most are very car-centric with little public transportation, I think it is fair to say that it is a disadvantage to have a car in downtown Paris. For one, the streets are narrow and parking is scarce (and very expensive!) which probably explains why people that do have cars typically own smaller-sized sedans or smart cars.
Lastly, I have to mention the world-famous TGV train, which is a high-speed rail service.
