The two programs focus on different roles. A CNS works in a healthcare institution (usually a hospital), specializing in the care of a certain population of patients. They sometimes provide direct care to the patients and may also promote optimal care of the patient by writing policies, developing programs, educating nurses, etc. that support the hospital and the nursing staff's care of the patients.
An educator focuses on teaching -- usually in a nursing school. The course content would emphasize educational theories, methods of teaching students, teaching skills, how to evaluate students, etc.
That's the short version. If you are considering a CNS role, you should search for threads on the CNS role (which varies greatly from place to place) so that you can learn more about it.