Son Goku is the main character in Dragonball, Dragonball Z, and
Dragonball GT. He is a pure blooded Saiyan (or Saiya-Jin). Goku was born on Planet Vegeta, and he was sent to Earth to destroy it, but lost his memory falling off a cliff. Goku was raised by Old Son Gohan. 

Goku married Chi-Chi and had two sons, Gohan and Goten. Goku was trained by Karin, Master Roshi, King Kai (or Kaiousama), and others. 

He was the first person to become a Super Saiyan. Goku fuses with Vegeta to become Gogeta and Vegetto. 

In Dragonball GT, he preforms a new Saiya-Jin level
called: Super Saiyan 4. 

Goku taught Goten and Chibi Trunks to do the
Fusion Dance to become Gotenks. 

He Killed Bebi using the Kamehameha Beam
in The Super Saiyan 4 Level. 

His Father is Bardock, a Saiyan who saw his cursed future. 

Goku is one of the Strongest Super Saiyans in Dragonball Z.