Hydrogen cars are cars that emit no fumes but only steam.
For driving the wheels there are electric motors like electric cars.
The difference is that, in these cars there are not batteries to store energy but fuel cells. The battery is there so that energy is not lost during braking because it is charged by it. The fuel is hydrogen which is stored in high pressure tanks made of carbon fiber.
As a fuel, hydrogen is a good energy carrier that produces electricity when it combines with oxygen as it passes through the cells. The only by-product that comes out of evaporation is water in vapor form.
These cars have the same range as conventional cars, but hydrogen is still expensive as a fuel and therefore not produced in sufficient quantities. The other downside is that they are low horsepower.
[Source: http://www.caranddriver.com]
