Basically, while you are spinning the reels like usual, you can trigger a bonus round/feature and start to play a completely different game.
Slot games with bonuses are a separate category and they can be summarized as “games within a game”. Yes, we are talking about slot machines with bonus games. All bonus slot machines have the same features: They are very easy to play, they offer satisfying payouts, and include additional games if you pick the right ones. Slot machines (especially slots with bonuses) are the most popular games at land-based and online casinos even in countries like Indonesia.