The Dragon Balls are mystical objects frequently used by the Z fighters. They were created by Namekians.
Earth Dragon Balls
If one gathers all 7 Dragon Ball's they can summon the eternal dragon, Shenron and grant a single wish within the eternal dragon's power. However, one must know the right password to summon the dragon or nothing will happen. Once they have been used they cannot be used for another year.
Namekian Dragon Balls
The Dragon Balls on Namek are very similar to that of Earth, however, they are much larger in size. The eternal dragon is known as Porunga. The Namekian Dragon Balls take only 180 days (a Namekian year) to return to normal. The chant must be spoken in Namekian to summon it and most importantly instead of having one wish you are granted three.
The Dragon Radar
As a youth Bulma created a radar that tracks Dragon Balls, which have been of great use to the Z fighters as it would take a very long time to track them without it.