A surge (or the faster “spike”) happen too fast, so reacting to a surge is no good. The zero-finesse surge protector is just a varistor placed between the power line and the ground line. The ground line (in this metaphor) is the floor around the sink, where all the overflowing water gets dumped. The other type of surge protector is essentially a “band pass filter” centered around 60 hz (the frequency of the current in the electrical grid). You can think of this as the “radio” of the surge protector tuning into the “station” of the wall outlet (and tuning out everything else).