REDOX Reactions

Oxidation is a process of losing electrons and becoming unstable.
Reduction is the process of gaining electrons and becoming stable.
This is a redox reaction because the two processes are occurring at the same time.
Oxidation can create free radicals. They are unstable because they lose electrons, so they try to steal electrons from other molecules like your cells. This damages your cells. Examples are heart disease and even aging.
So, oxidation can involve many things in our body. Two things that come to mind are oxidation of iron and oxidation of PUFAs.
Luckily, our body is amazing at neutralizing free radicals unless the body processes are overwhelmed.