Each icon has a unique value. The rewards for each symbol combination are listed in the paytable. Examples include 7, bars, bells, fruits, stars and other classic symbols. Many games use playing card values from 10 to A, as well as various themed images.
Scatter symbols
Unique in that they pay regardless of where they appear on the screen. Scatters can land anywhere and still award wins as long as the normal combination starts from the leftmost/rightmost reel and continues without interruption. In addition, three of them often trigger bonus rounds.
Bonus symbols
Activates slot features that increase players’ chances of winning. When players are given the opportunity to play multiple rounds for free, free spins are the most common alternative.
Wild symbols or Wilds
Wild symbols are common in slot machines. Their mission is to replace any regular symbol to increase the payout rate. So instead of just having one sign, the wildcard is made up of all the regular symbols depending on what the player needs at the time.
Expanding wild symbols, or expanding wilds
Means one symbol expands to cover the entire reel. It helps to get more wins.
Stacked wilds
Two or more icons are stacked vertically to form wild symbols.
Walking Wilds
During many spins, Walking Wilds remain on the reels. With each spin, they move forward in the same direction until they disappear from the screen.
Colossal symbols
Colossal symbols are significantly larger than normal symbols. They can expand to the full size of the reel layout, starting at 22. This is a popular choice, and some engines like GigaBlox are built around the concept of giant symbols.