Several image formats such as JPG, TIFF and PNG may contain extra information stored directly in the image.
For example will many digital cameras inject technical information such as which camera took the picture, the date it was taken, what aperture and shutter speed that was used and whether the flash was used or not. This information is often stored in a format known as EXIF information.
Similar to embedded EXIF information images may contain embedded IPTC information. IPTC is more focused on what the image contain, such as caption, headline and keywords. IPTC is widely used in news agencies, news papers and television.