This happens when reduction and oxidation combine. Reduction is the process of making something smaller than it already is, reducing it in degree or size. The redox reaction occurs when an electron is lost, but another is gained. When you lose an electron that's when you start to see oxidation, because you'll most likely notice that it's starting to rust, but when you gain more electrons, it reduces, because it starts to shrink in size or, smaller in degree. The Redox reaction stands for reduction oxidation. This is just a shorter way of saying that in this process you will see oxidation and reduction. Oxidation is also a loss of hydrogen, but reduction is the opposite of what is gained