Demo mode lets you get to know a game without using your balance. It runs on test credits that have no value and cannot be withdrawn.
When you switch to real money you may notice differences:
Balance: in demo you see test credits; in real play you see your account balance.
Currency: the demo may be shown in a currency different from your account's.
Bet limits: the minimum and maximum bet can be different. Demo mode often allows higher bets than real-money play.
What happens in a demo session does not indicate what will happen with real money: each round is independent. Before playing with your balance, check the bet shown in the game panel.