Because Barty Crouch uses Polyjuice Potion to impersonate Mad-Eye Moody for the entirety of the novel, it's unclear exactly how Moody-like the man Harry knows actually is--though Barty Crouch is able to fool Dumbledore, which suggests he did a reasonably good job. The fake Moody who teaches Harry is a surprisingly competent teacher and believes that the only way that students will be able to move forward in the world is by knowing as much as possible about what's out there. He teaches them about the Unforgivable Curses in particular and teaches them to throw off the Imperius Curse. Moody also tries to underhandedly help Harry win the Tournament by manipulating decent people into helping Harry and by leading Harry in the right direction. When Dumbledore discovers the fake Moody preparing to kill Harry after the third task, he discovers the real Moody locked in his own trunk. Madam Pomfrey tells Harry that Moody is going to be all right.