what is Slew Rate ?

I am not a audio specialist so I would like your suport: I have a Jeff rowland model 1 amplifier and i'd like to know what it's specifications mean: most things I understand, but what is the "slew rate"? It's specified in the manual: 70 volts per microsecond. is this what technically determines how quickly the amplifier amplifies a siganl from the pre-amp? In that case, is a smaller value better? How can this be described from an empirical viewpoint? Is this what audiophiles describe by "speed", as in a "fast" amplifier; my stereo sounds good to me, but in real life music sounds better. ...Of course it does! Actually, vinil sounds much more realistic than CD's, but still I notice a lack fullness and "fastness" of music coming out of my speakers. I would like to somehow improve this sound area of my stereo. Does the slew rate relate to these sound qualities or do I need to look elsewhere? I wish I could just audition different equipment and choose the one I like best, but living in Chicago, I have access to only those brands that my local shop provides. I need some criteria to narrow down my search. Great site! yours, Herman