Reduction

At the same time of oxidation, an atom of magnesium oxide, water, and a free electron combine to form a slightly different version of magnesium oxide.

This means it no longer needs hydroxide atoms, so it ejects it.

This type of reaction is called reduction.

More about reduction and oxidation

Some batteries use zinc as the anode and magnesium dioxide as the cathode.

When a flashlight is turned on, zinc gives up two of its electrons, leaving behind zinc ions behind at the anode. It is an oxidation reaction.

The electrons pass through the flashlight, turning the light on.

Then they enter the battery at the anode.

These electrons combine with magnesium dioxide to form magnesium oxide.

This is a reduction reaction.

To carry back the electrons from the cathode to the anode, inside the battery, charged ions flow through an electrolyte solution between the electrodes.

This completes the circuit and the power on the flashlight.

https://youtu.be/FyuDBDtHQZo?si=7XU4T0b-DHZws-6G&t=182. https://youtu.be/Wu3DlY9W0Dw?si=t2aycG-VRjjpv7Dy&t=233.