High Side VS low side

http://www.national.com/pf/LM/LMD18400.html

I do not understand what the High Side Drive really is doing?

It says on page 8 that high side drive can protect from being "energized"...
what is energized? The way I see the circuit is that if the load is to
high(low resistance) then there will be a lot of current and then the
circuitry can sense this and turn use some type of circuit limiting method?

If thats right then I do not get the low side drive. Looks to me, with the
circuit that is shown, there is no difference. Cause it just shows that the
load is shorted before the switch but I see the same can happen with the
high side(if it is shorted to ground before the switch in the high side
drive circuit)? Although is the current limiting is inside the circuit then
I do see a different... i.e., no way to short before the circuit limiting
circuitry.

Is this making sense?

Thanks,
Jon


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