"Redox" stands for reduction-oxidation. These are many chemical reactions that involve two different chemical species, one of which has its oxidation state reduced and the other that is increased. Redox problems can be broken into two half-reactions involving the addition and release of electrons.
One particular characteristic of most redox problems is that the identity of the elements other than O and H do not matter; only their oxidation states do! The species in question that are being reduced or oxidized depends on the number of oxygen and hydrogen atoms in the reactants and products, not on the species itself. However, not every redox problem can be taken as input (see the assumptions in the Details). To understand the redox balancer, first study the form of the equation. Each variable can be manipulated to get the intended number of each atom and each charge. "A" and "B" denote two different elements that stay the same "A" and "B" in the products. Also, do not forget to choose whether the reaction takes place in an acidic or basic medium.
For some redox problems to try, go to  or .
The initialized redox problem is reacting in acid. For a more comprehensive look at what redox is, see .