Goku is the hero of Dragonball Z, a good-natured and trusting soul. He is also the most powerful warrior on Earth and the first Super Saiyan in over 1,000 years. Having honed his skills and strengthened his spirit to a level never achieved by any being on Earth, Goku is able to fly, shoot energy beams from his hands, move at incredible speeds and, in a pinch, power up to a fighting level so high it creates an energy aura around his body. Goku hasn't learned these skills just for fun: his life is forced down this path as he battles the evil Saiyans in the final battle to save Earth.
When the Saiyans arrive it is a total shock in more ways than one. Not only does Goku meet his deadliest foe ever, but he learns the mysterious secret of his own past: he is a Saiyan formerly named Kakarot who was sent to destroy Earth. Goku's destiny is altered, however, when he is discovered in the wilds as an infant and raised by a peaceful wise man. A near-fatal head injury scrambles Goku's programming. Instead of growing up to become a destructive super-warrior, he becomes innocent and pure of heart, fighting only for good.
Goku is very protective of his family and friends and is always there to help them. If he has a weakness, it is his trusting nature. Goku is always looking for the good in people and can often find it where others do not. This costs him dearly when be believes that the Saiyan named Raditz has turned away from evil. Goku later pays the ultimate sacrifice to rid the Earth of Raditz.
Fortunately for our hero and for Earth, it's not the end of Goku. He is taken to the Upper World to train under King Kai in preparation for the coming of two even stronger Saiyans. The Dragonballs will summon him when the Saiyans approach Earth.
Goku has many powerful fighting techniques including the powerful Kamehameha wave and the Kaio-Ken, which he learns from King Kai. His most powerful weapon is an immensely powerful energy ball. This ball can only be used once and must be guided carefully, for it can destroy the planet if used inappropriately.
Goku's power level changes rapidly, rising from a 300 level in the early episodes to 5,000 after training with King Kai, to 8,000 when he is angry and to 21,000 when doing the famous Triple Kaio-Ken. And all of this is before his Super Saiyan stage. To further aid him, Goku still has the famous Nimbus Cloud and Power Pole.