Answer:
My teeth are sharp my back is straight to cut things up it is my fate.
I am a portal to another world which you cannot enter. Only you can see me but I can't see you.
I am a protector. I sit on a bridge. One person can see right through me, while others wonder what I hide. What am I?
I am three simple words everyone wants to hear. Three simple words such simple words and yet...life changing...
Although it sounds like I work on a transportation device I actually work in a restaurant.
The answer I give is yes, but what I mean is no. What was the question?