The Dragon Balls are a set of seven orange crystal spheres, with 1-7 stars within them. If all 7 are gathered together, and the spell to summon Shenron, the Eternal Dragon, is evoked, they will be granted three wishes.
Rules of the Dragon Balls
The seven Dragon Balls need to be in very close proximity (e.g., within the space of a large box) in order for their power to summon Shenron to activate. The incantation to summon him is "Eternal Dragon, by your name, I summon you forth: Shenron!" The first person to state their wish after having Shenron summoned will have it granted.
Wishes can only be granted by Shenron if he has the power to do so. Some wishes, such as reviving large groups of people (people can be revived as long as it's been less than a year since their death), use the power required of two wishes.
Other wishes that are against the rules include killing someone, making someone fall in love, and repeating a previous wish that was granted.
After the Dragon Balls are used, they will turn to stone, and scatter across the Earth, remaining dormant for one year before they are permitted to be used again.
Porunga, the Namekian Dragon, can be summoned once every 130 days (the Length of a Namekian year) He must be summoned with a Password in Namekian. He can revive someone regardless of how long it's been since they died. He grants three wishes. He can revive the same person multiple times.
Dragon Balls in #ss3
The Dragon Balls have been used to make wishes many times in the past. Previously, the most recent wishes on them were made by Suu, who used the wishes to undo the damage done to Akihabara by Hazel Ninegate and resurrect the people she killed. On January 8th, 2015, they were used again to repair the damage to Tokyo caused by Ashagar the Endbringer and revive the ones he killed on that day, with one wish held in reserve. The second wish was made on January 24th, 2015, when it was wished that any beings from plenums of concern as designated by Simon Kerrick would be routed first to rei.bot, no matter where she was, for her to admit or dispatch as she saw fit.
Currently, the balls are inert and cannot be used until January 24th, 2016.
The Namekian Dragon Balls were used for one wish to revive Daniel Kakaku, Katerina Markov, and Haneka Tadashita on January 29, 2016, with Kailey Ninegate holding the other two wishes in reserve and taking the balls to an undisclosed location. The remaining two wishes were used by The (3rd) Intern on June 7th, 2016 to bring the AU Actuary's War Machine to the site of an ambush at Anima Persis and to rescue Hino Rei. The balls scattered and begame inert, and will be findable again in another 130 days (Dec. 5, 2016)