i just grabed this from sewie's link
Difference to full time symmetric 4WD is that a "4-low" setting is not available in AWD cars. Due to the lack of "low range" AWD vehicles are less capable in off-road settings than full time 4WD vehicles, but work perfectly well in easy off-road environments and on-road.
Recently some new
"automatic" AWD systems have emerged. Fancy names like "Real Time 4WD" or "active AWD" are hiding the fact that they are essentially sophisticated 2WD systems.
Automatic asymmetric AWD would be the best term for them.
AWD =
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