A recorded image is an interpretation of light and objects. When you shoot a compressed video, that interpretation is created by a camera company; when you shoot RAW that interpretation is made by you!
Like a photographic negative, a raw digital image has a wider dynamic range, or color gamut, than the eventual final image format, and it preserves most of the information of the captured image. The purpose of raw image formats is to save, with minimum loss of information, data obtained from the sensor and the conditions surrounding the capturing of the image (the metadata).
This allows the user to interpret the information and, in turn, the look of the images captured. Things like color temperature, image sharpening, contrast curves, and black levels can be set very specifically and reset over and over again. This gives the filmmaker a wider latitude of post-production options.