Stand-by and Hibernate are two slightly different computer states.

The Stand-by state will keep the computer at bare minimum power, enough to keep your programs running in the background, yet put the computer to sleep, which just happens to be another term for the computer's stand-by state.

When you put your computer to sleep, it's like a college kid doing his term paper, then falling asleep at his desk. His head just plops down on his desk, and onto his books.

When he wakes up, just like a computer, with a simple poke of your finger, he wakes up, and he's able to resume where he left off in his term paper, and, as odd as it is, just like a college kid who wakes up from his sleep state in some instances, Jaws has a poor reaction to the stand-by state after a while, particularly if you put the computer in stand-by for too long, you'll find that the computer will start to lag, and/or Jaws will start to behave strangely.

Now, in the case of hibernation mode or state, you are essentially shutting the computer down, but placing a bookmark on where you were with your work. The computer literally shuts down, notes what the computer was doing at the time, it's condition, open programs and the like, writing all this information onto the hard drive and powers down, so that when you come back to the computer, it will start up, and you'll find your work is still out waiting for you.

Now, the important thing here is that in stand-by mode, you cannot unplug the computer and carry it around with you, as in the case of a laptop, where you might want to place it in stand-by to go do something else, then come back to it, after you've been invited to a study party at a friend's house. The minute the computer loses power, the stand-by state is terminated, and all the data you were working on will be lost.

Not to mention, you will be doing some irrevocable damage to your hard drive by shutting down the computer improperly, like power outages do.

This is not the case in hibernation mode, as you can unplug your laptop and carry it around with you without fear that you'll be damaging the hard drive, as it will essentially shut itself down.

You get the best of both worlds here, especially with the portability factor.

The other benefit is that if the computer loses power for any reason, your hard drive is parked, and therefore any bumps will not damage it, which is not the case if you place your computer in stand-by mode.