Welcome to the most basic trick in magic. A performer takes a coin, puts it in the palm of their hand, and then opens their palms out to you. The coin is gone. If the performer is wearing long sleeves, you can usually guess what happened to it, but sometimes they're not - so what happens then?
There's nothing more mysterious going on here than a little glue trickery. A thin coating of glue on the back of the performer's hand will hold the coin. They never really put it into their palms.