There are all types of AWD.

Generally 4WD is used to mean vehicles with part time 4wd where you
wouldnt want to use it on anything but very slippery surfaces and dirt
roads don't count.   These vehicles with also have a transfer case with
a low and high range.

There ARE 4wd vehicles that are AWD and come with a transfer case.  For
that you need a limited slip or other means to allow the front and rear
axles to not quite turn at the same speed without burning out or blowing
up your drive train.  With few exceptions, the true offroaders in this
class will also have two speed transfer cases.  Most will also have at
least limited slip on the rear axle and limited slip in the transfer
case...  Those tend to be very nice for higher speed highway driving
where you might also run into really slippery stuff occasionally, as
they always have at least some drive on all four wheels.  Kinda like an
Audi.  Some also have locking transfer cases and/or axles standard, some
as aftermarket addons.  Those tend to be for serious bad trails.

Ground clearance is as important as any of this.  An old Citroen jacked
up can go most places anything but a hardcore 4x4 will.

Oh, and water tightness might be a factor if you fail to stop before you
hit that fishing hole.  You can buy snorkel kits if you must do your
fishing in drive thru mode.

Some of the better crossovers can also do much of what you are looking
for, and may have a better ride quality.

Or you could invest in the lottery and when you win, buy a Range Rover
Turbo HSE or a Turbo Cayenne or a Mercedes G-Wagen and tour the highways
in excess of 150 mph, yet still be able to jump sand dunes off road.

Try here for some background info:

http://wiki.answers.com/Q/What_is_the_difference_between_an_AWD_and_4WD_vehicle

bear in mind that most AWD vehicles are not really meant to be
"off-road" vehicles, due mostly to ground clearance issues.

Also AWD was developed from race cars where it helps get power to the
road for high-speed cornering

4WD or 4x4 was of course created for serious off-road use