Here is a list of all documented files with brief descriptions:

libexif
_stdint.h
exif-byte-order.h	Defines the ExifByteOrder enum and the associated functions
exif-content.h	Handling EXIF IFDs
exif-data-type.h
exif-data.h	Defines the ExifData type and the associated functions
exif-entry.h	Handling EXIF entries
exif-format.h	Handling native EXIF data types
exif-gps-ifd.c	Info about GPS tags
exif-gps-ifd.h	Info about GPS tags
exif-ifd.h
exif-loader.h	Defines the ExifLoader type
exif-log.h	Log message infrastructure
exif-mem.h	Define the ExifMem data type and the associated functions
exif-mnote-data-priv.h
exif-mnote-data.h	Handling EXIF MakerNote tags
exif-system.h	System specific definitions, not for installation!
exif-tag.h	Handling EXIF tags
exif-utils.h	EXIF data manipulation functions and types
exif.h	Exif/exif.h
i18n.h