for details of photographic terms please see my thread on digital photography -
http://www.banglacricket.com/alochon...ad.php?t=23128
RAW is an image format used by dslr as well as bridge digital cameras that provide full manual controls. please note that canon bridge cameras like the s or a series don't have RAW anymore.
pictures taken in raw format contain as much data as the ccd or cmos photosensor can pack in. these RAW enabled cameras usually come with a manufacturers raw converter that you can use later to adjust white balance, sharpness, contrast, curves and a variety of other functions. i'd really suggest reading my link above as i wrote a guide to digital photography in simple terms.
if you really want to manipulate tiff you shoould think about buying adobe photoshop or photoshop elements. gimp is a free version offered for linux.