The Fusion Dance is a dance that lets the users fuse.
Revealing of the Fusion
When Buu was terrorizing Earth Goku decided to teach Goten and Trunks the fusion dance. He had to teach them to they could fight Buu. When it was his time to go back to the Other World he told Piccolo to continue teaching them. He accomplished this and the fusion between Goten and Trunks created Gotenks .
The users must be perfectly symmetrical and have equal power levels for this to work. The ending point is when both users point there fingers touching each other. This must be symmetrical. If not it will create a weaker form of the fusion.