well, while i can't give you a straight edge answer about the actual GI stuff, I strongly suggest you check out the stickied posts at the top of this forum! and search for "scales"!
an amp is basically that - it takes the signal from your bass and fires the amplitude so that it can be audible!
a pre-amp is used to "edit" the signal before it is amplified (i think??) i.e., add bass, treble... etc...
an active bass reqiures a battery, should it be an active preamp it will change the bass' signal before it reaches any part of the amp for further equalization!
a passive, does not require a battery.
an easier defination would be that in an active system, the signal has bass/treble etc ADDED to it, where as in a passive, the bass is simply removed...
however, check out the amps forum!! the GI is for music theory!!!
welcome to TB!