This document defines some key terms related to slot machines: - Bonuses are special features of slot games that award extra payouts or spins. They vary by game. - Pay lines are the lines across the reels that must match symbols to win. More pay lines are available with higher bets. - The theoretical hold percentage is how much of deposits a slot will pay out over time, usually 95-97%. This is specified in documents from manufacturers. - The credit meter displays available credits to play, but players can lose track of spending, so starting with coins instead of loading a card is advised.