Free radicals--the root cause of many diseases

Scientists and medical researchers have disclosed that at least 70 chronic degenerative diseases such as heart diseases, cataracts, asthma, joint pains, rheumatism, aging, parkison disease, Alzhemier's disease etc are associated with free radicals. Though there may be other theories but so far the free radicals theory seems to be more readily acceptable. As reported in Science Daily (May 5, 2008)that according to the research done at University of Melbourne with ARC Centre of Excellence for Free Radical Chemistry and Biotechnoloogy, it seems to suggest that nitrate free radical could be a real cuplprit for respiratory diseases however more researches are required to ascertain this finding. what is free radicals in plain language ? May be I will try to state this in coming posting