Every Fruit Machine has a Nudge Feature, other features that must be present for a fruit machine to be considered a fruit machine include Hold, Gamble Feature, Cash Ladder & Bonus Trail.
There are other Fruit Machine Features but the ones listed above must be present for a fruit machine to be classed as a fruit machine.
The Nudge Feature allows the player to nudge one or more reels on the next spin, sometimes the player will be awarded a number of nudges and will be able to nudge several of reels thus increasing the chance of making a winning combination.
Nudges are also awarded during the Bonus Trail feature and are used during the main part of the game. When going around the Bonus Trail, it's possible to gain as many as 4 or more extra nudges depending on the specific fruit machine game being played. The nudges show up on the payline ( win line ) and give you the chance to better the outcome that is showing on the reels. You can not only earn bigger cash prizes but you can acquire symbols that are needed to trigger the Bonus Trail feature.