Dragon Balls? What's that...
In the complete series, the Dragon Balls play a major role throughout the majority of Dragon Ball, Dragon Ball Z, and Dragon Ball GT.
In Dragon Ball and Dragon Ball Z, the Dragonballs are a collection of seven golden crystal spheres each containing a different number of stars numbering from one to seven which are used to grant the summoner a wish. Though after the summoner's wish has been granted, the Dragon Balls scatter across the globe and cannot be used again for a particular amount of time. The number of wishes (ranging from 1-3), power of each wish, and the time between successful summonings (going from 130 days to one year) depend on the set of 'Balls used - to see more rules go HERE. When the creator of one of the sets of Dragon Balls dies, the balls wil instantly turn into stone until a new successor can take his place to revive the dragon. To find out more about each set of Dragon Balls and their properties HERE.
In Dragon Ball GT, the Dragon Balls have a much different appearance. The set of 'Balls used in this anime-only series was created by Piccolo before he split into Kami-sama and Piccolo Daimaio. These Ultimate Dragon Balls (a.k.a. Black Star Dragon Balls), have some rather unique properties. For starters, these balls scatter across the entire universe after being used, rather than just being scattered around the globe. In addition, the Ultimate Dragon Balls put so much strain on the planet on which they are used that they must be returned to that planet within one year or the planet will be destroyed! Finally, the wishes granted by these Dragon Balls are so powerful that they cannot be reversed by any other set of 'Balls.
What wishes are made with these 'Balls?
Throughout Dragon Ball and Dragon Ball Z, the various dragons are summoned 14 times for a grand total of 22 wishes. At the moment, we don't have any data pertaining to the wishes that take place in Dragon Ball GT. You can read a detailed chart of every wish including who made the wish, where the wish was made, what was wished for, and any failed wish attempts that were made HERE.