Many people said the gambling is just a game and another people said it is Investment. How do you think? 
Correct, I agreed on that gambling is really just a game of relax not a kind of business investment.
It is usually, losses of money.
Its very simple like you say - but its difficult to explain to the addicted gamblers who only think of their wins and cant stop even after they win a big because their greed wants more - and that greed s never satisfied. It is possible to control your greed and not gamble like crazy. Then it remains a mode of entertainment by paying the casino owners - in that way.