Here is a super neato table that helps makes sense of the various antioxidants and where to find them.
Antioxidants work by acting as an electron donor to a free radical, which is basically an out of control molecule that causes cellular damage because it has an unpaired electron. Cellular damage and mutations are linked to pretty much every ailment possible including cancer, neuromuscular disease and degenerative diseases. When an antioxidant molecule donates its electron, it neutralizes the free radical.
Vitamins can act as antioxidants as well including vitamin C and vitamin E; but be careful with mega doses, they can also cause damage, basically negating any good effects they may have.
P.S. It only took about 19 times to get this damned thing to load right, so there is a little extra love in this post:)