newb question....what is RAW?

I may be getting a new camera for U/W snapshots. I am leaning heavily towards the Canon A570IS. Someone mentioned that the A570IS can be 'hacked' to operate in 'RAW'. I've seen the term RAW thrown around in my short time in this corner of Scubaboard, but I'm not quite sure what RAW is (other than underdone meat). My question probably indicates I'm a rather novice photographer, as most of my pics are taken very casually

Here are two good explanations. PM me if you have any further questions. Happy to help.

Raw image format - Wikipedia, the free encyclopedia

RAW vs JPG

To a new photographer, or a guy like me who dives two-four times a year, RAW can be a life saver. After the dive you can easily adjust white balance, exposure value +-2 stops without screwing the picture up. The manipulation is done easily in a RAW converter program like the old RAWshooter or new programs. I've seen experts use Photoshop to change Jpegs in a similar fashion but I've never had the time or patience to go past simple adjustments of Jpegs. RAW is easy and it will bring color back to otherwise cyan filled photos and allow you to brighten the image up without introducing a lot of noise.

Raw is all of the digital data that the lens imprints on the sensor. When you shoot a JPEG, the camera decides what the picture should look like, processes the information and gives you the picture it thinks you want. If you shoot a truly terrible picture, completely underexposed and black for instance, that's usually what the camera will give you in JPEG form. It picks out what it is programmed to see as the critical information and throws away the rest. I've taken those types of pictures into photoshop, and what I got out is crap. I've taken similar pictures in RAW. One strobe was behind a rock, and the other one didn't fire. Oh, and by the way, the subject was that special fish you've only seen once and never got a picture of. The one that darts away and you only get one chance. Take the black picture and convert it on your RAW conversion program. Crank the brightness all the way up. Add fill light. Adjust the contrast, reset the white balance. You've still got a crappy picture, but it is a picture. Now take it to photoshop, adjust the levels, sharpen, create a couple of layers to improve the background and brighten the shadows. Wow-that's not bad. This is why I stopped shooting JPEG about the same time I learned how to set my camera manually. With practice and a good RAW converter, you can repair almost anything and make it look decent. When you're as bad a photographer as I am, that's worth the hours of processing time and the gigabytes of memory the files take up on your computer. Even the 7 seconds you have to wait on your p & s camera to take the next picture because the file is so big it takes forever to write it to the card. Thankfully, really expensive DSLR's have a huge buffer that will take 10 or 15 RAW shots in a row, as long as the strobe has time to recycle. (And take 8 gig cards that will hold a couple of hundred 14 bit RAW files). Now, if I only had a housing for mine. (or a little more talent, so I could get the shot right the first time in JPEG.)