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Jaggies: Jagged-looking artifacts created in digital photographs or a digital television picture, caused by poor image or video processing.  Jaggies frequently occur in objects with vertical and diagonal lines when the camera pans from left to right.  See Motion Artifacts.
 
JPEG, JPG: Joint Photographic Experts Group.  The jpg abbreviation is used for compressed image files produced with the JPG standard, the most ubiquitous compressed image format.  It is the default image file of almost all digital cameras.  See Lossy Compression.