Slot machines operate under the principle of RTP. RTP or Return to Player is a term describing how much of your bet you can earn back. If RTP is at 80%, you can expect to receive 80 dollars on average, per 100 you invest. Modern slots, both online and land-based ones, are programmed to have a specific RTP value. Machines with the highest RTP pay the best theoretically, but the number is calculated over millions of spins, so a high RTP doesn’t guarantee that you’ll get back your money every time.