A mechanical device that uses three, four or five, and sometimes more, circular reels of different sizes is a slot machine. Each of the reels has several symbols, usually painted on and the most common designs are bars, cherries, the number seven and a jackpot symbol. The more modern slots operate by computer programs that select the winning combinations randomly. The percentage of winnings, as well as the odds, is normally set by the manufacturers of the program and millions of spin combinations are possible.
Theme designed machines are very popular, with everything from wildlife to a more patriotic themes. Many times, the casinos will do a whole room in a particular theme and use slots, such as poker slot machines or video one, as well as any other casino game, to further compliment the theme slot.
There are different types of slot machines, such as the three or four reel games. Common sense tells us that lining up three matching symbols on such a machine to win, rather than having to line up four, is much easier. To match four can be very difficult, even on liberal poker machines. And of course, three sevens can be hit more frequently than four sevens on a 4 reel machine. If possible, try to play on three reel machines.
Most slot machines have the center line as the pay-line and only the correct combinations on that line will pay. However, such a machine may have the 3 pay-lines in the center, bottom and top of the window, so that means that any correctly lined combination on any one of those 3 pay-lines will win. There is an advantage to playing the 3 paying games, as you are given extra chances to win and can get up to triple payouts if they are in the correct order and show on more than just the one pay-line.