Well on cars,The C.P.S. is fitted to tell the E.C.U. when to 'fire' the spark plug,basically like a Contact-breaker set-up (points) on old type ignition system.
When piston is at T.D.C. the sensor triggers the E.C.U. to tell the Ign.Coil to discharge,Causing a spark.
Camshaft position sensor is to tell the E.C.U. when to operate the fuel injectors. This can also be done with Crank sensor,but with V.C.T. (variable cam timing) it isn't accurate enough.
Hope this helps!