Son Goku is the main character in the dragonball series. He is referred to as Kakarot (or Kakarrot) by his rival, Vegeta. Son is the title inherited from his adoptive grandfather, Grandpa Gohan, or just Son Gohan. The prefix grandpa is used to avoid confusion with Goku's first son, Gohan. He is the second son of Bardock, with Raditz being the first, and Fasha is speculated to be his mother.more...
Goku is the only pure-blooded Saiyan to have a pure heart, due entirely to falling down a deep ravine and banging his head. Being a saiyan, he survived the fall, and his naturally violent nature disappeared, and became a good person because of his Gohan's good influence.
Goku is also the only saiyan to achieve every level of Super Saiyan. He becomes a super saiyan at the end of the Freeza saga, a full-powered super saiyan during the Cell Games Saga, and learns Super Saiyan 2 and Super Saiyan 3