It is the ability to work the heart and lungs to maximum capacity for longer periods as well as being physically and emotionally healthy.
You present an interesting picture of health, but there are minor challenges that can be raised.
I discourage patients who are not professional athletes from pushing the heart to maximal capacity (heart rate calculated by Key pulse formula) for more than short periods of time.
Maximal heart function stress should be done only if approved by a physician after stress test heart analysis.
The key pulse is usually 80% of maximal predicted pulse. I find for most it is better to keep within 10% of the key pulse for workouts and to slow down significantly if the pulse is at or past predicted maximum.
It is safer to work out longer periods of time than short maximal workouts, for general health purposes.
Otherwise, I like your interpretation. In fact the second part of your description is adequate, “being physically and emotionally healthy.”