Tien is a good friend of Goku. He just like Yamcha and Piccolo appeared in the DB series. He like Yamcha and ChaoZu are minor characters which means the dont really play a large role in the DBZ series. He also helps fight the Saiyons but gets killed by Nappa and is sent to King Kaios to train.
He later appears in the Cell Era but gets beat up. He like Yamcha and ChaoZu kinda faded out as characters.