Where is the difference between TM and a normal mantra meditation?

Hi,

I have a question:

What makes the difference between NSR(TM) and a normal mantra meditation described in various books?
What defines TM? Is it the Mantra, the Posture, the time of Meditation ...

I also can not differentiate between the term "restful alertness" used by NSR(TM) and "relaxation response" used by Benson. Where is the difference?

Maybe someone can bring light into this.

BR,
Nick