Re: from my understanding
Antioxydants bind with free radicals, which to my understanding are an electron that was knocked out of its orbit. When free radicals are thus neutralized, they are stopped from the cascading effect of kicking off more electrons and creating more free radicals, leading tissue damage.
Perhaps this is a simplistic explanation, but from what I understand, free radicals are created from oxydants, and are actually useful in some senses because they depose of unhealthy tissue along with the healthy. For instance, Miracle Mineral Supplement is an oxydant, and some experts believe that flaxseed oil has its anti-cancer effect at least in part because it oxydizes in the body.
Free radicals are also created in response to heavy metals interacting with tissues. So if we have a large heavy metal load and are trying to detox from metals, it's wise to take in a lot of antioxidants to minimize the effects of the free radicals that are set into motion by the mobilization of metals from tissue.
Such antioxydants would come from vits C, E, Bs, turmeric, and beta-carotene from vegetables.
A healthy, fresh foods diet will give you the antioxidants you need, unless you are chelating metals, in which case you should be sure to get lots of antioxidants from supplements as well.