Not quite. AWD has a transfer case with an open differential, so that the back wheel and the front wheels can turn a different speeds. Some vehicles can actually switch between RWD and AWD.

4x4 has a transfer case with a locked differential, so that you get more traction. But this should only be used on loose surfaces because on solid roads you can damage the transfer case leaving it in 4x4. Some vehicles have a "part-time" 4x4 that switches the transfer case to unlock the differential, giving you AWD that won't damage the transfer case.