Peter, since semi or sushi haven't had a chance to jump in on this and you did say "slightest knowledge", let me say that slew rate is the rate of change of its output voltage(in volts per microsecond,as you indicate)that an amplifier is capable of. The significance is that the maximum frequency which an amplifier can reproduce with negligible distortion is proportional to the slew rate divided by the peak output voltage which the amp has to supply. So, slew rate is an important engineering consideration, but once an amp can reproduce at least 20,000hz with low distortion at its designed peak output voltage(which any properly designed amp can do), the slew rate is necessarily shown to be high enough for audio purposes. In particular, a higher slew rate doesn't mean that an amp is "quicker" in reproducing music and isn't of any particular significance in the real world.
