Hi. I also, am new to using MosFETs/drivers. The impression that I have is that, if you are using them at high frequency (in my case, 100kHz flyback converter), that the drivers supply enough current to quickly charge the GS capacitance and reduce the turn on and off times to increase switching efficiency. This assumes that the uC output would have been high enough to turn the MosFET fully in in the first place. If that doesn't apply, then the driver would also provide the voltage to do that.