Inertial Reference relates to the motion of the aircraft; the system can detect speed and acceleration. These are outputs for navigation.
Inertial Navigation uses the reference computations in the process of navigation - requires a computer; INS normally have an IRS within the overall system.
Navigation requires positional knowledge - an essential input for navigation and for some systems aligning inertial platforms.
Where am I (where have I been), where do I wish to go. Positional predictions can be made based on acceleration, speed, and direction - where am I actually going.
Navigation control can be achieved by comparing the desired destination with that predicted - what the aircraft is actually doing.