‘We know induction motors suffer from slip’. It wouldn’t be appropriate to say so, because the slip is necessary for the induction motor to rotate continuously. I believe Niels, in his answer, has also mentioned the same thing and also stated rightly that permanent magnet (PM) motors do not work with slip. Both motors rotate, but the reason behind the action that causes them to rotate are slightly different. Let me try to answer the question

Intuitively if you are wondering why and how?

Why the PM motor doesn’t work with slip:

A PM motor has two independent magnetic fields, one from its stator armature (supplied by AC) and one from the permanent magnet rotor (i.e.if the model is a rotating field and stator armature type, like many smaller permanent magnet motors)

The PM motor’s alternating current-induced field on the stator is continuously rotating (of course, since you have AC that’s what happens). It’s almost like the effect of the north and south pole magnets physically rotating in a circular fashion, but in this case, only their fields move, not the stator itself (which is why it’s called stator).

Anyway, now you’ve established a rotating ‘virtual magnet’ if I can call it that. We know magnets repel or attract other magnets, so we put permanent magnets on the rotor with opposing poles.