Thumbnail Image is generally in reference with web pages. It is the miniature of the original image. The image may be a graphic or page. One of the purposes of thumbnail image is to decrease the bandwidth and time taken for download. If you shrink the original images with HTML or client-side scripting, the visual quality of the image will be poor with no saved bandwidth. Ideal is to use a smaller copy of the image rather than shrinking. When used for desktop printing, these help to manage better a group in a layout.