"Generally speaking, we could mention four different types of online slot machines. These include video slot, progressive slot, classic slot, and mega spins. We can say that classic slots are online slot machines that aim to imitate the look of the real slot machine. They are a traditional approach to the slot machines. Many people prefer classic slots because it reminds us of nostalgic feelings. Usually, classic slots have more straightforward rules like lining up three lemons or cherries on a three-reel slot. They typically have traditional pay tables without additional free plays or bonuses. While playing online slot games if you see that the game offers you bonuses, stories, and hundreds of paylines, you could guess that the game is a classic slot.
source:
https://riversweeps.org/different-types-online-slot-machines/"