Goku is the son of a third class Saiyan warrior, named Bardock. When he was a baby he was sent to the planet Earth to destroy all intelligent life and make Earth suitable for sale to the highest bidder. All Saiyans have a brutal nature, have an instinct to fight, can transform several times and have a tail so they can turn oozaru, a giant ape, and become ten times as strong as they were when they see the full moon. Before Goku reached Earth his home planet, Vegeta, was destroyed leaving only 4 Saiyans alive, including Goku. When Goku reached Earth he was found and adopted by an old man, named Gohan. Gohan couldn’t control Goku because he was very aggressive and constantly screaming.  

Goku was trained by a lot of people like: Gohan (who taught him martial arts), Master Roshi (who taught him techniques as Kamehameha), Korrin, Kami, King Kai (who taught him techniques as Kaio-Ken and the Spiritbomb), and he also trained himself for an immeasurable amount. Goku's trademark attack is the Kamehameha, he is the first to use this attack but later on other characters like Krillin, Gohan, Goten, Trunks and Cell use this attack.  

Later Goku found out about his origin, that his real (Saiyan) name is Kakarotto and he learned about his father and his brother Radditz. When Goku was born his power level was 2, but he is the first in 3000 years to turn into a Super Saiyan, he was the second to reach Super Saiyan level 2 and he was the first to reach level 3 and 4. Later Goku reaches power levels of over 500 million.

Goku destroyed two of the four surviving Saiyans, Radditz and Nappa, and occasionally fuses with the last Saiyan, Vegeta, to form Vegetto and later Gogeta. Goku is, without a doubt, the strongest fighter in the universe, of course Vegetto and Gogeta are stronger fighters but they are fusions.  

Goku dies a lot of times and was almost every time wished back by the dragonballs. When Goku and his friends won another great battle all seven dragonballs were absorbed into Goku and Goku’s body disappeared, leaving nothing but his clothes on the ground.