Who wrote candide and what were the main ideas put forward in that work?

Voltaire was the author of "Candide." The main concepts were that not everything was "for the best" and that suffering for its own sake was not always a noble endeavor. This was in comparison to the thinking of the day, advocated for by Leibniz, who was a major proponent of Optimism, which did hold that suffering made it easier on others.