Dragonball Episode Guide:

Dragonball
The first anime based on Toriyama's manga, it lasts until the battle with Piccolo Daimao ends. It focuses more on humor than action, quite unlike the following two anime.

Dragonball Z
When the first series ended it's run on TV, the manga was still being produced by Toriyama. Wanting to tap into the comic's success, a new series was created known as "Dragonball Z," which continued the story of Son Goku and his adventures.

Dragonball GT
"Dragonball GT" was produced mainly for one thing: money. When Toriyama finally ended his massive manga, the TV executives decided to go on without him. Dragonball GT proved to be a moderately successful series, but by this time Dragonball had become stale in Japan, and it ended relatively early.