Vejiita's and Bulma's son. Appears the first time when coming from the future to warn Gokuu and friends about the coming of Cell and the androids in 3 years (and save Gokuu from dying, who because of the use of teleport has aquired a heart disease. He first appears, when Cyborg Freeza and Great King Cold appear, killing both. He often during the series carries a sword and uses a capsule corp. jacket.
I can say that there are two Trunks:
o The "future" Trunks, who because of his tough life is a lot stronger (in his time he lives in constant fighting so this gives him a lot more training, making him one of the strongest of the series) and also makes him more polite;
In his future all of the earth population (including the Z warriors) had been killed by the androids (except for Gokuu who had died of heart disease provoked by his teleporting tecnique). Hence, Trunks travels 20 years back in time to give medicine to Gokuu and warns the Z warriors about the coming of the androids (he comes back from the future at the same time that Cyborg Freeza and great King Cold appear, killing them both; Trunks knew that by this time, Gokuu would have returned to Earth. Afterwards, Trunks goes back to his own time, but returns again three years later to help the Z fighters battle the Artificial humans. During his stay in the present, he becomes extremely strong, being stronger than any of the Z warriors (excluding Gohan and maybe Gokuu). After Cell is killed by Gohan, Trunks returns to the future and kills the cyborgs #17, #18 and Cell (in his future #17 and #18 seemed to be stronger), that terrorized his future.
o The "present" Trunks is not so strong or polite as his future self,- this always gets himself (and his friend Goten) in trouble. During the Z warriors fight against Buu, Trunks fuses with Goten becoming Gotenks, a very powerful character.