For the given reaction of hydrogen burning, we can complete the sentence as:

Hydrogen reacts with oxygen to produce water. 

To be more precise, 2 moles of hydrogen reacts with 1 mole of oxygen and yields 2 moles of water. An important aspect to note here, hydrogen and oxygen are both gases, while water is a liquid. So not only are we getting a new product, there is phase change as well and 2 gaseous reactant combine to yield a liquid product. This reaction generate a polar molecule, in which covalently bonded hydrogen and oxygen share electrons. Since oxygen is much more electronegative as compared to hydrogen, the shared pair of electrons are actually very close to the oxygen molecule, making it a polar molecule (positive and negative charge centers separated by some distance).

Hope this helps.