what is the difference in 4 wheel drive and all wheel drive?

It is generally the same.

For a car having more than 4 wheels (which is quite rare) this is where all wheel drive makes sense.

cheers

The Subaru's All Wheel Drive system is very sophisticated. All of the wheels do not necessarily "drive" at the same time. It can act like a front wheel drive car or a rear wheel drive car depending on surface traction and what you the driver are wanting to do at the moment.

By definition they're the same thing, but manufacturers typically label them like this:

AWD is used for vehicles that have an automatic system that usually has front wheel drive until the wheels slip or lose traction, then power is automatically transferred to one or both rear wheels. In higher-end performance models, it does this on acceleration. This is usually for cars and cross-over SUVs.

4 wheel drive is driver-selected. The vehicle is usually rear wheel drive until the driver selects 4WD, then all 4 wheels receive power at the same time. This is usually for trucks and off-road vehicles (like Jeeps).

cars with 4 wheel drive can be changed from 4 wheel to 2 wheel drive and all wheel drive cars can't be changed. they use all wheels, all the time.

A four wheel drive you can put it in 2 high and have only two wheels turn and all wheel drive is all the time you cant turn it off.

4wd generally have a transfer case with 4hi and 4low gearing, they may or may not have a center differential, without a center diff they cannot be driven in 4wd mode on dry pavement. AWD always have a center diff, and are pernamently engaged with warious viscous coupling or electronic clutch mechanism sending the power to where its needed. For rock crawling or mudding, go 4wd, for road, snow, gravel and light off roading, go AWD.