1 The Namek
The original form of Kami-sama and Piccolo-daimao. When the Namek was to become Guardian of Earth he was forced to split from his evil self, thus creating the two previously mentioned Namekians. Kami-sama is pure good, while Piccolo is pure evil.
Piccolo-daimao was imprisoned within a jar for several centuries before he escaped. Muten Roshi attempted to re-imprison the demon, but was killed in the process. Kami-sama attempted it as well and instead he himself was imprisoned. Goku was forced to
destroy the Daimao, but before his death he reproduced, spitting out an egg which sprouted into a new and stronger Piccolo.
Kami-sama was the Guardian of Earth until he was forced out of necessity to recombine with Piccolo, thus creating the Super Namek. Kami-sama was the creator of the Earth dragon Shenron, and it's accompanying Dragonballs.
Dende was a young Namekian who had studied to eventually become a Guardian himself. After the creation of the Super Namek, Dende is brought to Earth to become its new Guardian. His first assignment was to recreate the Dragonballs and Shenron. He
managed to give Shenron a slight power-up, but did not have the time to complete the process to make him equal with Porunga. Later on he is able to complete the process.
2 The Four Lesser Kaios
3 Each galaxy of the universe has an accompanying Kaio. Each Kaio is a martial arts master, possessing many extremely powerful skills. The four Kaios periodically gather at the planet of Dai-Kaio (The Grand Kaio) for martial arts tournaments.
The most notable Kaio is our own Northern Kaio (The Kaios are of the North, South, East, and West Galaxies) who aided much in Goku's early training. He was killed when his planet is destroyed in an attempt to defeat Cell.
4 The Dai-Kaio
The Dai-Kaio is an unrivaled fighting genius set above the four lesser Kaios. He plays host to many martial arts tournaments, and his world is a massive training ground for the valiant dead of the entire universe.