To bleach something is to remove or lighten its color; a "bleach" is a chemical that can produce these effects, often via oxidation. Common chemical bleaches include sodium hypochlorite, or "chlorine bleach," and "oxygen bleach," which contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate or sodium percarbonate. "Bleaching powder" is calcium hypochlorite. Bleaching may be a preliminary step in the process of dyeing.
圖片參考:
http://upload.wikimedia.org/wikipedia/commons/thumb/b/b6/Bleach-bottle.jpg/150px-Bleach-bottle.jpg
Commercial chlorine bleach