The difference between free pokies and free spins is an important distinction.
Free online pokies are slots that you can play as much as you want, for as long as you want. If the machine tells you you've run out of money, it's as simple as pushing a button or refreshing the page to top your balance back up. Since you are playing for free, you also can't win any money.
Free spins, on the other hand, are typically used as a casino bonus, and are limited in amount. If you claim a bonus for 50 free spins on Cleopatra, the spins may not cost you anything, but everything else still abides by real money rules. Any winnings earned during free spins are yours, but when you run out, you're back to paying for every spin, like you would with normal real money play.