A Namekian came to Earth due to a violent cataclysm on his home planet Namek. His name was long forgotten, only known as the Nameless Namek. When he came to Earth he knew he wanted to be the next Guardian of Earth, but the current guardian sensed evil inside of him. Kami had to split himself into to entities of the good and the bad. King Piccolo was the offspring of the split.
Kami became the Guardian of the Earth while King Piccolo wanted to rule it. In order to guard the Earth, Kami instinctively created his own Dragon Balls and the eternal dragon Shenron. The end of King Piccolo came when Goku killed him, but not before King Piccolo released an egg that hatched into Piccolo Jr., who while different, was still one being with Kami.
Major Story Arcs
When the Saiyans came to Earth, Raditz proved to be more than a match for both Goku and Piccolo. In order to defeat him, Goku sacrificed himself. When the stronger Saiyans Nappa and Vegeta arrived, Piccolo's power still proved to not be enough. When Nappa attempted to kill Gohan, Piccolo sacrificed himself. Since they were the same being, Kami departed to the Other World as well.
While in Other World, Kami gave Chao-Zu his body back and sent the other Z-Fighters who died in the battle - Yamcha, Tien and Piccolo - to train with King Kai. When Piccolo was revived by the Namekian Dragon Balls, Kami returned to life as well.
During the Cell Saga, Piccolo has no other choice but to fuse with Kami to return to their original fused power level. They take Piccolo's form since it is more youthful. He returns to his full power and becomes The Namek. Krillin joking around tries to find a new name for him so he says things like Kamiccollo. The Namek was not amused, but to save everyone from confusion he decided that they can still call him Piccolo.
Kami leaves the position of Earth's Guardian to fellow Namekian Dende.
Powers and Abilities
Kami as the other half of King Piccolo can be considered his equal in terms of power. Kami as the guardian of earth is in charge to keep the planet safe. As a member of the Namekian Dragon Clan he is vastly powerful with energy and mystical attacks. Kami at is introduction was shown defeating Goku quite easily and trained him for three years to be ready for Piccolo.
Explosive Wave - A burst of energy fired from the casters body to repel any attackers.
Evil Containment Wave - A magical move that allows the user to trap an opponent inside a small object like a bottle or electric rice cooker.
Eye Lasers - Kami can fire a thin yellow beam from his eyes. This can be used as a quick strike or to nullify an oncoming energy attack.
Flight - Kami can fly under his own power.
Instantaneous Movement - Kami is able to teleport to at least King Yemma's domain without using energy or needing to sense where he is teleporting.
Magic Materialization - Kami is able to conjure objects out of thin air.
Possession - A seemingly unique ability, Kami possesed Shen to enter the 23rd World Martial Arts Tournament.
Regeneration - Due to his Namekian heritage Kami can regrow limbs and regenerate wounds.
Self Destruct - Kami can convert his life energy and overcharge himself to take out an opponent at the cost of his life.
Telekinesis - Kami can move objects with his mind.
Telepathy - Kami can communicate via telepathy