Fusions
Fusion Dance: This fusion involves two fighters who perform the fusion dance, but one fighter does it the opposite or mirrored to the other character. The characters must around the same height, build, and power level, or if one is stronger, he can lower his power level to have the same as the other. This type of fusion lasts for exactly 30 minutes, and then they have to have a one hour break before they can fuse again. Goku learns this dance when he was up in the heaven between the Cell game and Gohan's first year at Orange Star High School. Only fore of the characters can fuse like this. Goten and Trunks fuse to fore Gotenks, and Vegeta and Goku fuse to form Gogeta who is the most powerful fighter in the three series. He is also known as the "Ultimate Saiyan".
Potara Fusion: This fusion is done with special earrings called the Potara Earrings. This fusion is supposed to be way better then the fusion dance and was originally used by kaioshins. The two characters who wish to fuse must put one of the earrings so one character wil have it on his right ear, and the other on his left. After putting on the earrings the characters can now fusse into the new character. Unlike the Fusion dance, this fusion is a permanent fusion but eh character defused because of an unexpected condition. Each character can only do this once in his life, and Goku was supposed to fuse with Gohan but he got aborbed by Buu, so Goku fused with Vegeta to form Vegetto.
Namekian Fusion: This fusion is done by Nameks only. There is no dance or earrings, they simple put their hand on the other Nameks chesk and they fuse into another character. You can defuse depending on the character you fused with, but in most cases, you connot. Piccolo and Nail fuse in the Frieza saga, and they are allowed to defuse unlike Piccolo and Kami who were originally one being.