Goten is the youngest son of Son Goku and Chi Chi in the anime series Dragonball Z, invented by Akira Toriyama. Apperantly he was "left" with Chi Chi right before Goku died in the Cell Games. He is friends with Trunks, the son of Vegeta and Bulma, and was able to reach the level of Super Saiyajin at the age of 8, the youngest ever to reach this pinnacle of Saiyajin power.
He fought in the world martial arts tournament the same year he first became Super Saiyajin, and made it all the way to the finals of the junior division before being beaten by Trunks. On that same day, he helped Trunks save Vegeta from Majin Buu.
Soon after, Trunks and Goten merge into a single person, Gotenks, and reach Super Saiyajin Level 3, the only person to reach this level besides Goku himself.
Goten acts very much like Goku did when he was young, always laughing and playing, and very rarely serious about anything.