If you use the Hurloon Minotaur to attack your opponent, it attacks with a power of 2. If she doesn't block the Minotaur, your opponent suffers 2 damage, which is deducted from her life total. If she blocks the attack with a Benalish Hero, the attacker confronts the blocker with its power and vice versa. Thus, the Minotaur deals 2 damage to the Hero, which exceeds the Hero's toughness of 1, so the Hero dies. The 1 damage dealt by the Hero isn't enough to kill the Minotaur, though, so the Minotaur survives. Because the Minotaur was blocked, it didn't damage your opponent at all, even though it dealt more damage to the Hero than was needed to kill it.