Hydrogen is a gas that can be used to power cars and other machines instead of relying on fuels like petrol or diesel. A hydrogen prize is a type of competition in which people are challenged to come up with the best way to use hydrogen to power cars. The person or team with the best idea will win a prize. It is a way to encourage people to come up with better and more efficient ways to use hydrogen to power cars and other machines, so that we have cleaner air, better energy, and a healthier environment.