A hydrogen reformer is a type of machine that makes hydrogen gas. It uses a fuel like natural gas, gasoline, or diesel and combines it with water and air to produce hydrogen gas. Inside the reformer, the fuel and air mix together, and a catalyst helps turn them into hydrogen and carbon dioxide. The hydrogen gas is then used for various purposes. For example, it can be used as fuel for vehicles like cars and buses that use hydrogen fuel cells. It can also be used to make other things like fertilizer or chemicals.