Earth Dragon Ball
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Teh Earth Dragon Balls were created by Kami and later re-created by Dende. Seven Dragon Balls existed, and they could be used to summon Shen Long when they were gathered together. Shen Long could grant any one wish within its powers as long as it did not kill, create love, repeat a wish he had previously granted, and a few other restrictions. Legitimate wishes included eternal youth, immortality, bringing back a scorched forest, or even recreating a destroyed planet. It was also possible to return a person to life, although they had to meet certain criteria such as dying of an unnatural cause (murder for example) or dying within the past year (if more than one person). Each individual could only be brought back once. Shen Long would grant the first wish uttered after he had been summoned by whomever was present.
When Dende became Planet Earth's new Kami, he modified the burnt out Dragon Balls created by Kami (which transformed into seven ordinary stones when Kami fused with Piccolo) giving Shen Long the power to grant two wishes (though in the Buu Saga of the English manga, it was labeled as three wishes). In addition to this, the second wish could be saved for a later time. This was shown in the Boo Saga when one wish was made to revive all those killed by Majin Vegeta and Son Goku then asked Shen Long to save the second wish for later. Therefore, only four or so months after Kid Boo's defeat, another wish was made to erase the Earthlings' memories of Boo. One obstacle that Dende put in place on the new set of balls, however, is that – like the Namek Dragon Balls – the summoner must utter a set of words. In Dragon ball Z, these words were "Eternal Dragon, by your name, I summon you forth: Shen Long!" In Dragon Ball GT, right before the Shadow Dragon Saga, the words were changed to "Arise, Shen Long!"
It is debated whether Dragon Balls can revive artificial life or not. The revival of Artificial Human No. 17 during the Cell Games Saga does not apply because he started out as a Human and was made into an Artificial Human by Doctor Gero. Artificial Human No. 16, who was killed by Cell, was not seen again in the series even after the wish was made to revive all of Cell's victims. Furthermore, when Kid Boo annihilated Planet Earth and everyone (except the evil ones) were wished back, Artificial Human No. 8, who was a purely mechanical Artificial Human like No. 16, was seen giving Goku energy for his Genki Dama.