What was the purpose of Alchemy?

Soooo many books had been written about Alchemy and Alchemists in the Muggle world. So many of Chelle's favourite books, indeed. This was one question Chelle had no problem answering. Her hand shot up in the air.

"Professor, Alchemy has varied uses. It can be used to convert stuff into precious metals such as gold and silver. Alchemists also spend a lot of time looking for ways to make the Elixir of Life through Alchemy," Chelle replied. After a short pause, she continued, "Many years ago, a famous Alchemist, Nicholas Flamel, was known to be in possession of the Philosopher's Stone and was a few hundred years old, or so I have read."