Hydrogen is the first element on the period table. It's light, small, and the most abundant element in the universe. Its ionized form, H+, is synonymous with a proton.
It comes in many forms, and can be described many ways, but it was named originally for its contribution to the water molecule, H2O. Hydrogen translates, from its Greek roots, to "Water forming."
When hydrogen burns by interacting with oxygen in the air, it becomes water. This makes it an ideal fuel, because it releases energy without contributing to carbon emissions.