For a fixed impeller diameter and speed, the pump has a predictable performance curve.
Where the pump operates on its performance curve will be determined by the characteristics of the system in which it is to work. The operating point is where the performance curve and the system curve cross.
The system curve represents all of the losses caused by friction due to the piping, elbows, valves and other physical components in the system.
The system curve is parabolic as its values are related to the square of the flow rate.
Pump and system curves cross and throttle shifts
the operating points