Stall/Surge
From a technical point of view:
Stall is, like a stalled wing, separation of airflow on the compressorblade(s).
e.g. axial flow too low in relation to hi rotational speed, mostly on 1 or limited stage(s).
a stall can develop in a surge, meaning the airflow thru the engine can completely stop
or even reverse its direction....flames coming from the intake.
In GE/CFM the VBVs protects the Boosterstages from stall - by increasing the axial flow through the booster -
and the VSVs protects the core compressor by adjusting the 'angle of attack' of the vanes.
(P&W and RR by bleed valves to increase the axial flow and fewer stages of HPC/IP variable)
Pre FADEC generation engines are more sensitive to stall/surge,
with the modern FADEC engines there is a stall recovery scheduled in the ECU/EEC.
P&W and RR are more sensitive for stall/surge but can withstand it better than a GE/CFM,
while the latter is less sensitive.
During ground run, you will notice an unstable and roaring N1 (Fan Stall) before a compressor stall will develop,
a compressor stall comes with a loud bang and with or without rising EGT.
(depends on the reaction time of the operator)
A surge (never experienced from cockpit but from outside) with load bang(s), flames from the intake,
unstable parameters N1/N2, rise of EGT (as being told) and eventually blow out.