The Dragon Balls are a small or large, depending on what planet you’re from: Earth or Namek, opaque and translucent. They are shimmering balls with each one having one to seven stars in each that can grant any wish. However, it has been proven wrong that they can’t grant just any wish, but we won’t get into that. When the wish is granted, Shenlong, the dragon of the balls, returns back into the balls, goes into the sky, and scatters across the plains and cannot be used, until the time limit is up.
However many wishes you make, the amount of power used, and the time between each granted wish, depends on what Dragon Ball set you have used. When the creator or caretaker of the Dragon Balls has died or been absorbed and gone, the Dragon Balls turn to stone, and cannot be used, until a new caretaker is brought forth and revives the dragon.
There is a difference between the Dragon Ball and Dragon Ball Z Dragon Balls, to the Dragon Ball GT ones. This had nothing to do with Toriyama Akira’s set of Dragon Balls, and was made up from TOEI only. These balls were created by Piccolo before he split up between the good and evil of him. The Black Star Dragonballs/Ultimate Dragon Balls, have other qualities, different from the original. For example, when the wish for these balls are made, they travel across the universe, rather than the four corners of earth. Also, when the balls are done traveling across the universe, there has been so much strain and power on this, that the earth cannot handle it, and must be brought back within a year, or the earth will be destroyed. Plus, the power of these balls are so great, that the balls wishes cannot be taken back or reversed.