There are two categories of slots, one is high volatility slots and the other is low volatility slots.
A high volatility slot is a slot which compared to a low volatility slot has a higher risk in it. These slots usually have a big winning which you can be lucky to get after many spins. In these slots, you can hit the spin button many times without winning anything but when you finally win you win a big amount which happens occasionally.
A low volatility slots can allow you to win more frequently when spinning the reels but the winning amounts are lower compared to the winning amount in the high volatility slots.
High volatility slots are best to play when you have a lot of time to waste and a decent amount of coins to play with. It is all about building up an excitement whilst waiting for the big winning. And this is just what makes these slots more satisfactory and fun to play.
As mentioned earlier, the low volatility slots have a lower risk and since you win more frequently in these games you will feel more eager to hit the spin button and continue playing. Sometimes you do get a big winning in these slots also, although this is more likely to happen in the high volatility slots.
So which one of these should you play? It all depends on how much money you are willing to spend. If you have a lot of money to spend you can try out your luck in the high volatility slots which can reward you very well.
If you have less money to spend then it might be a better idea to play in low volatility slots where you get smaller winnings more frequently. But of course, this is all up to you in the end.