EXIF stands for Exchangeable Image File Format and it is a widely accepted standard for storing interchange information in image files. EXIF block usually occupies a few kilobytes in each JPEG photograph. It may contain tiny preview image of the photograph—thumbnail.

EXIF specification defines tens of tags along with their types and meanings. Such tag-value pairs are basic elements of the EXIF block. Most of those pairs is optional in EXIF: they may or may not be present. This is why EXIF information differs among different camera models.
Although EXIF data varies it usually consists of many useful details, like shutter speed time, aperture settings, date and time, ISO speed, focal length, exposure program and bias and many others.

In addition to standard fields EXIF specification provides place for manufacturer specific information (so called MakerNote). Unfortunately its format is not defined and digital camera makers are rarely willing to disclose details of MakerNotes.
ExifPro can decode MakerNotes of a few digital cameras, thus camera specific columns in the details view.

To find more information regarding EXIF specification please visit exif.org site.