We are exposed to oxygens all the time, we can’t avoid that. With time an apple ages and becomes brown and shriveled. Why? Because of oxygen exposure.
The same thing that happens to an apple happens to our body – just a lot slower. Anti-oxidants help us to slower that process.
An antioxidant is a molecule capable of slowing or preventing the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Oxidation reactions can produce free radicals, which start chain reactions that damage cells.
Antioxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions by being oxidized themselves. As a result, antioxidants are often reducing agents such as thiols, ascorbic acid or polyphenols.
If you add lemon juice to the apple it will slower the process of oxidation. It will not become brown that fast. If you translate this metaphor it means that more anti-oxidants can help us to stop the aging process too.