The real and online casinos have a collection of intimidating slot games that you can explore one by one. It was only a couple of decades ago when “slot machine” referred to a simple mechanical game that had three reels with pictures of fruit. Today the slot machines are diverse and come in so many varieties. Some common slot machines include classic slots, 3D slots, fruit machines, progressive slots, mobile slots, and multi-pay slots. You can also find free-to-play versions of all these types of slot machines. Before you step into the gaming floors, make sure that you know about the RTP and the rules of a slot machine.