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 slot machine, as well as any other casino game, to further compliment the theme.
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 a slot 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.
Some casino slot games show three pay-lines located in the center, bottom and top of the window. That means a winning combination lined up on a slot machine correctly on any of the pay-lines will win. Other slots show the center line as a pay-line and to win you have to have a paying combination on that pay-line only. If any winning combination shows up two or more times together, then you can earn double and triple, which is one advantage of three paying games.