Hydrogen is the most abundant element in the universe, however, on Earth it is not found in free form, but rather combined with other elements, such as with oxygen forming water (H2O), with carbon forming hydrocarbons, or with other elements forming a infinity of different compounds.
Hydrogen is a versatile and non-polluting energy vector, that is, it is an energy carrier, in such a way that it can be subsequently released in a controlled manner. From it, you can get heat and electricity.