Found this online to explain --
Digital cameras save JPEG
(.jpg) files with EXIF (Exchangeable Image File) data. Camera settings and scene information are recorded by the camera into the image file. Examples of stored information are shutter speed, date and time, focal length, exposure compensation, metering pattern and if a flash was used.
Use EXIF as a learning tool
Many camera owners study EXIF to compare successful photos to those that are not. Data provides insight about how camera settings affect photo characteristics such as exposure, depth-of-field and subject movement.
EXIF is read by applications that support JPEGs. They include web browsers, image editing and organizing programs and some printer drivers. The printer drivers use the information to automatically enhance images, which can result in a better looking prints.
Exif data is very helpful to let you "see" what your camera setting were when you took the shot.