File extension JPG is related to JPEG (Joint Photographic Experts Group) image file format. It is mostly used for bitmap images (photos, pictures, etc.).
Image files that employ JPEG compression are commonly called JPEG files. Most image capture devices (such as digital cameras) and most image editing software programs that output JPEG files are actually creating a file in the JFIF and/or Exif format．
The most common filename extensions for files employing JPEG compression are .jpg and .jpeg, though .jpe, .jfif and .jif are also used. It is also possible for JPEG data to be embedded in other file types - TIFF encoded files often embed a JPEG image as a thumbnail of the main image.