Key Terms to Know. Words like "return to player" (RTP), "volatility," and "paylines" are crucial for understanding how various games work. While voind+slotslatility reflects the degree of risk involved in a given game, RTP is the percentage of wagered money that a slot machine is designed to return to players over time. Whereas low volatility slots offer smaller wins more frequently, high volatility slots may offer larger payouts less frequently.