For Mirrodin! is an ability that appears on Equipment. When an Equipment with For Mirrodin! enters the battlefield, you create a 2/2 red Rebel creature token, then that Equipment becomes attached to the token. You don't choose a target—the token arrives and the Equipment is already attached to it.
This matters because Equipment usually needs a creature already on the battlefield to be useful. For Mirrodin! gives the Equipment its own creature, so it can attack or block immediately and start contributing. If the token leaves the battlefield, the Equipment stays put and can later be attached to another creature. It's a reliable way for red and white decks to add pressure and board presence without needing extra creature cards.
