There are two kinds of slot machines: straight slots and progressive slots. Straight slots pay a predetermined amount. On the other hand, progressive slots have a jackpot that grows by a percentage of each coin played. This jackpot can often build up into an enormous amount before someone wins it. 

Slot machines vary on denomination of coins, the number of reels, how many coins to play, and single or multiple paylines. Quarter and dollar machines are the most popular. Some casinos have "big spender" areas where you can bet up over $100 per machine using special tokens.

The odds of winning are determined by the number of reels and how many symbols are displayed on each reel. The result of each spin of the reels is determined by a computer that generates random results. This holds true for both online slot games and slot machines found in casinos. The machines are set by the casino to generate whatever payout they choose. The greater the number of reels and symbols, the harder it is to win. Most machines are set to pay out anywhere from 80 to 98 percent of the coins that are played in a pay cycle. With some machines, the number of coins played is directly proportional to the payoff. Some machines don't even pay a jackpot on one coin, and the three-coin jackpot often pays 150% of a two-coin win. It is almost always best to play the maximum number of coins the machine allows. For multi-lined payline slot machines, a coin has to be played for each payline in order to get paid for a win.

Each casino's payoffs will vary. If you win the jackpot then you'll be paid by a casino employee, instead of directly by the machine.

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