Approx. two weeks ago, I noticed my engine light stayed on. I took my vehicle to a reputable auto shop in which they told me that once they put the vehicle on the diagnostic machine, it problem was the CAM shaft sensor.

First question, what is the CAM shaft sensor and the purpose?
Second question, will my vehicle eventually shut down?

For a couple weeks after I had the cam shaft senor replaced, the engine light turned off. Now its on again. Please advise. Thank you.