system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: The basic plot of Dragonball Z and why it is so popular.
gpt
Dragonball Z is based of the show DragonBall which is about a boy called Goku who is sent from another planet to destroy it. He hits his head when he arrives and that causes him to lose his memory and thus forget his mission. Goku has incredible strength and is great fighter as his home planet celebrated fighting.

Dragonball Z take place when Goku grows up and has a son of his own. It follows the already epic story that is Dragon Ball and uses the same characters and settings. It's about Goku journey to save the earth and usually involves him collecting 7 magic balls (Called dragon balls) so that he can make a wish. A key point is that you can only make the same wish once. Goku usually save the word by beating people up.

Dragonball Z is so popular because it's basically a giant soap opera with fight scenes.  The characters are quite well written for anime and develope as the story goes on and their always fighting (Although it's mostly posing for a fight.)