Goku is the main character in Dragonball, DragonballZ, and Dragonball-Gt. He is the most powerful fighter in the world. He got training from some of the best trainers ever. Goku meets a lot of friends and enemies. His best friend is Krillin. Other good friends of his are Yamcha, Tien, Piccolo, Kami and there is a lot more. Goku is actually a Saiyan. He fights a lot of enemies. Some of the most powerful are Vegeta, Frieza, Cell, Buu, and Beby. He marries ChiChi and has two sons. They are Gohan and Goten.
Once a very power Namekian named Kami wanted to become guardian of Earth. But first he had to shed out all of the evil inside of him. The evil took form as Piccolo Daimaou. He wanted to take over Earth but Goku killed him. Before he died, he spit out an egg. The egg is a new Piccolo. Piccolo wanted revenge against Goku but he never really did. First they had to work together and then he trained Gohan. Over time Piccolo turns into a good guy. In GT he kills himself to save Earth.
Vegeta is from a royal family of Saiyans. The first time he came to Earth was when he wanted the Dragonballs, but he lost. In Namek he joins Gohan to help fight Frieza. Even though as the series progresses he turns into a good guy he still has one goal. To be better then Goku, but he never actually does. Later on, he has a lot of respect for him, too.
Gohan is the first son of Goku and ChiChi. He is very powerful and when his dad gets hurt he gets even more powerful. Gohan is a great addition to the team. He has helped then on more then one occasion. Goku wants him to be a great fighter, but there is one problem, ChiChi wants to him to be a great scholar.
There is two Trunks in DBZ. First there is the one from the future. He warns the fighters about the androids and gives Goku some heart medicine. He also helps in the fight against Cell. The other Trunks is from this timeline. He is Gotens best friend. When they fuse they turn into Gotenks. Gotenks transforms to SSJ 3. He is one of the teams most powerful fighters ever.
He is the trainer of Goku, Krillin, and others. When he was young he was the worlds most powerful fighter. But now he is an old perverted man. In Dragonball he trained Goku and Krillin in some very unusual ways, but look at Goku now. Master Roshi made Gokus signature attack. None other then the great Kame-Hame- Ha.