Pilots actually fly the aircraft, and in single-seat aircraft, obviously have to do everything else as well: comms, navigation, sensor tasking, weapons (or other payloads) control and release, yadda yadda yadda. Think F/A-18C/Es, AV-8s and F-35s.
In aircraft that require Naval Flight Officers (F/A-18F, EF/A-18G, E-2, P-3/P-8/P-6, etc.) pilots still do all of the actual stick and rudder work, but will split the mission-specific load and operation of all the various and sundry on-board systems and mission tasks with the NFO(s). How much and to what extent is platform specific, as is the number of pilots and NFOs in the aircraft. The E-2/C-2s and the "big wing" land-based aircraft with large crews also have enlisted Naval Aircrewmen (NAC) who might handle sensors, expendables, perhaps SIGINT/ELINT portions of the mission, or serve as crew chiefs, loadmasters, door gunners, SAR swimmers, etc. as well.
No NFOs in helicopters, but I think all have at least one enlisted NAC who may have multiple tasks to perform.
All aircraft obviously need pilots. Many require NFOs and/or Aircrewmen as well due to mission complexity and platform specifics.
Thus endeth today's VERY basic lesson.