Alkaline Water Facts

Well the answer to your bolded question is that redox potential refers to the relative likelihood that an atom or molecule can lose or gain electrons and change their oxidation state. Oxidation is losing electrons to gain a more positive formal charge, whereas reduction is gaining electrons to reduce positive formal charge. This is most easily seen with iron in hemoglobin – iron (+2) is normal hemoglobin and can bind to oxygen readily. If it loses an electron it becomes iron (+3) which is the oxidized form, and can no longer bind to oxygen effectively (methemoglobinemia).

In reference to your water question, nothing is realkly being oxidized or reduced in the formal sense, because hydrogen atoms in a water molecule are formally (+1) and when the water is split to make acidic protons or basic OH (-), hydrogen is still in (+1) oxidation state, so no redox reaction is occuring. The only redox reaction that can occur with hydrogen is if you start with hydrogen gas (H2) which has hydrogen in the (0) oxidation state, and then oxidize it to hydrogen (+1) by reacting it with oxygen gas (O2) to make water.