User blog:BalrogLune/Ultra transformation?

Can someone help explain to me about the mechanism of transforming host to Ultra? I have Ultraman, Ultraman Tiga, and saw some episodes of Ultraman Max and I'm confused. How does the transformation work?

Does the host actually become the Ultra or do they just swap places? I know some ultras have their own human form but the ones that don't, I just don't understand how it works.