What causes a CD to skip when playing?

I've been told that if you spray a little furniture polish like pledge and wipe it dry with a t-shirt it will fill in the scratches and stop most of the skips. It works on small scratches but if the scratches are really bad, nothing that I've tried of will stop it. I've been told that if you spray a little furniture polish like pledge and wipe it dry with a t-shirt it will fill in the scratches and stop most of the skips. It works on small scratches but if the scratches are really bad, nothing that I've tried of will stop it.