The Dragonballs are located on Namek(old and new) and Earth. The Namek ones will always be more powerful than the Earth ones.Piccolo/Kami brought the Dragonballs to Earth being the first Nameks on Earth. Kami became the Guardian of Earth and Piccolo a great warrior.The Dragonballs can be used to revive people from the dead and anything you want by summoning one of the Dragons once you have all 7 Dragonballs.