Uses:
Selenium is used in the glass industry to decolorize glass and to make red-colored glasses and enamels.
It is used as a catalyst in many chemical reactions.
Selenium is used in solar cells and photocells - in fact the first solar cell was made using selenium. It is also used as a photographic toner.
Selenium is used with bismuth in brasses and as an additive to stainless steel.
Despite its toxicity, selenium is also an essential trace element in the animal and human diet. It has a goldilocks-like quality that you must not be exposed to too much or too little of it, you must get the right amount.