There are three types of fusions introduced in the Dragonball Z/GT Series. These are: Permanent Fusion, Temporary Fusion and Namekian Fusion. All these fusions are introduced in the Dragonball Z Series. Fusion is mainly combining two fighters physically. When combined they have more power than the power of a single fighter. This comes in handy in many times when a villain is hard to be defeated.

Permanent  Fusion:
This type of fusion cannot be broken and as the name says is permanent throughout your life. This fusion is done through weraing two identical majical earrings called the Porta Ear-rings. Bothe the fighters who are going to fuse take a Porta Ear-ring and wear it. When both the fighters have worn the ear-rings the fusion occurs and there is no looking back on this. The fusion is permanent and cannot be broken. There has been only one Permanent Fusion in the whole series and this was the fusion of Goku and Vegeta into Veggeto. Veggeto was winning over Super Buu but he deliberately got absorbed into Super Buu so that he can rescue the other fighters. This somehow wore off the permanent fusion and Goku and Vegeta came back to their ordinary selves.

Temporary Fusion:
This fusion is done by the Fusion Dance. This fusion is only temporary and lasts for only thirty minutes. After thirty minutes the fusion wears off and the fighters come back to their original selves. This type of fusion is seen more often during the Series since this is the easiest. But also the fighters must be of equal strength. Also, if the fighters are in high rankings of strength, for example, if the fighters are both in the SSJ4 stage, then the span of fusion reduces and lasts for only twenty minutes. The most seen fusions of this type are of Goten and Trunks to form Gotenks and Goku and Vegeta to form Gogeta.

Namekian Fusion: But there is also another type of fusion. This is the way through which Piccolo and Nail fused to stop Frieza. Nail is dying and he tells Piccolo to fuse with him. Piccolo lays out his hand on Nail and a bright light is seen. After that Nail isn't present. Both Piccolo and Nail had fused. This is the old way before Goku introduced the Fusion Dance in the Buu Saga.