A fusion is when two people form into one. There are three ways to do this: Number one, do the fusion dance; two, wear special earings; and three, absorb them like Piccolo did to Nail on planet Namek.
Fusion Dance
Gogeta (on the left) is the fusion of Goku and Vegeta; Gotenks (on the right) is the fusion of Goten and Trunks. Here are some points on this fusion dance.
The two fighters have to be about the same size, weight, and power (that means that if one of the warriors is stronger, he'll have to lower his power level to the other fighter).
Even minor mistakes in the dance can cause a defective fusion.
This fusion will only last for 30 minutes and when they seperate, the two fighters must wait one hour before they try to fuse again.
Potara Fusion
Here are pictures of Vegetto, the fusion of Goku and Vegeta wearing Kaioshin Earings. These earings are also known as Potara Earings. And here are some pointers.
