When starting out in photography, a lot of photographers are confused about RAW and JPEG formats while shooting.  Its easy to explain but being photographers, its easier for us to comprehend a visual reference.  I've had the option of shooting RAW since my Canon 20D over 10 years ago and even though I never shot JPEG again, I never actually compared a RAW with JPEG to see the data I would've been losing if I let the camera compress the files itself...