ExifTool is a command line application which extract exif data from photos (eg. jpeg file), available on Windows and Mac OS X, you can download it from here. Windows GUI is available as well.
What is exif data? The exif data in a digital photo file store information about the photo and camera which include date, time, caption, camera, lens, focal length and a lot more.
If you upload your photos on flickr, you can check the exif detail information. The ExifTool is an easy way to extract exif data from the photos.
After install the ExifTool, execute the program from Terminal or command prompt:
$ exiftool photos.jpg
ExifTool Version Number : 8.23
File Type : JPEG
Camera Model Name : Canon DIGITAL IXUS 60
I just list a few exif data here. If you use the exiftool, there is a lot more information available.