Goku is a saiyan warrior that descended from Earth from the planet
Vegeta. He was eveil at first, but when he smashed his head, his memory of the saiyan race.
Vegeta is the saiyan prince of planet Vegeta. Once Goku and Piccolo
killed Raditz, Vegeta and Nappa set out to kill Goku. When fighting, Vegeta fled to the planet Namek to find the dragon balls
and make himself immortal. When they were fighting Frieza, Vegeta teamed up with them only with the reason that Frieza destroyed
his whole planet. Vegeta later marries Bulma and has 2 kids, Trunks and Bra. (one in DB, one in GT)
Non-chibi Trunks is one of the only survivors of his dimension of
Earth after Android #17 and #18 anihillated anything they saw. He took his time machine and went to warn Goku about the androids.
Gohan or "SaiyaMan" is a half human / half saiyan warrior. His dad
is Goku and his wife is Videl. They have a daughter named Pan.
Goten is a half human / half saiyan warrior. His dad is Goku and his
brother is Gohan. He is able to fuse with Chibi Trunks to form Gotenks. Goten was able to transform into a super saiyan way
before Gohan or Goku did.
Yamcha, Tien, Chiaoutzu, and Krillin:
Yamcha is human and was originally a desert bandit but turned out
to be a good guy. In Dragon Ball, Yamcha tried killing Goku for the Dragon Balls. Tien is human also (even with
the 3 eyes) and he fought Goku in the World Martial Arts Tournament. Krillin is Goku's best friend, and Krillin helped Goku
with his fights ever since they were kids. Chiaoutzu is Tien's best friend and tries to keep up with the others, but
Chiaoutzu is not strong, although.
Goku's past arch enemy, Piccolo is a namekian that is Kami's
evil counterpart. Later in DB, Kami and Piccolo fuse together to defeat the androids. When Gohan was little, Piccolo
and Gohan formed a friendship. Piccolo was the one who trained Gohan to becoming a warrior when Nappa and Vegeta were arriving.