exposure is determined by 3 factors on a dSLR. shutter speed, aperture, and ISO.
shutter determines how long the shutter is open for - longer means more light. aperture means how large the opening is, and ISO is film sensitivity - the higher the ISO, the more sensitive.
if you want to read more, there are plenty of tutorials and explanations on the net...
as for RAW. this is the format that the camera stores the information take in.it doesnt do anything in itself. but in order to print email the image etc, you will need to convert it using a raw converter.. any camera that comes with RAW ability, should have a software converter as part of the package. photoshop can also convert raw.