Superhuman Durability is a super power that most beings with super strength possess. People who possess this ability are usually highly resistant to deadly force. For example, a bullet fired from a gun would have little or no effect on them.
Superman is incredibly durable, and he is often referred to as invulnerable. But actually he isn't quite invulnerable. He can still be harmed by others with strength levels close to his, and he can also be harmed by magic and Kryptonite.