Fusion Information

Fusion = when two people come together to make one stronger being. There's only 3 ways to fuse in DBZ

Fusion Dance
two people do a special dance to come together. Vegeta and Goku do it to become Gogeta, and Trunks and Goten do it to become Gotenks. This fuse lasts 30 minutes.

Earrings
two people put on special earrings (one on each person) to fuse. Goku and Vegeta do it to become Vegeto. It's permanent.

Namek Way
Only Nameks do this, and it's permanent. The people hold each other's hands to fuse. Piccolo fuses with Nail, and later with Kami.