Trunks

Father: Vegeta
Born: Earth
Race: Saiyan
Future Trunks comes from the future, duh..., and helped the Z Fighters in many ways. He has the Tapion Sword, and chopped Freeza in half. He went Super Saiyan, during the fight with Freeza and King Cold. He also helped them in the fight with Cell. He come to the Z Fighters in a time machine, mainly to give Goku medicine that if he didnt take would kill him in the future. He saved Goku's life and many others.
His battles in Dragonball Z were against Cyborg Freeza and King Cold, Cell, and Buu(I think).

Trunks(Small)

Father: Vegeta
Born: Earth
Race: Saiyan
Chibi Trunks is much like Goten in many ways. They are probably best friends and are equally matched. Trunks is born after the Cell Game, but before the Buu Saga. He first turned Super Saiyan at about the age of 7 or 8.
Trunks is only able to help fight Buu. He is one of the major characters in the GT saga.