A RAW file is sometimes referred to as a true digital negative. The option to shoot RAW is available on most advanced and professional digital cameras.
With a RAW image file, no processing is done by the camera (such as sharpening or white balance). This gives total control to the photographer when he or she post-processes (edits) an image. You have more latitude to controlling exposure than with JPEG files. A RAW image has a smaller file size than a TIFF.
The RAW format, considered essential by professional and serious photographers, is still not widely used by others. At this time, RAW files can not be opened with every image editor and can take longer to process when editing. Many digital camera users find JPEGs, when shot at the highest resolution and lowest compression settings, meet their expectations for image quality.
Since there is no accepted standard format for RAW files, each manufacturers format is different. Images in this format have a .raw extension, eg: filename.raw.
Adobe, developer of image editing programs as Photoshop and Photoshop Elements, is calling for a single standard, open source format for RAW files between camera manufacturers. The new format is called Digital Negative (DNG).