Here's why:

* Oxidation is a chemical process where a substance loses electrons. This often involves the gain of oxygen atoms or the loss of hydrogen atoms.

* Reduction is the opposite process where a substance gains electrons. This often involves the loss of oxygen atoms or the gain of hydrogen atoms.

Think of it like this:

* Oxidation is like taking something away (electrons).

* Reduction is like adding something back (electrons).

These processes always occur together in a redox reaction. One substance is oxidized while another is reduced.