Well, you may probably do this kind of search when you are in need of other similar photos of your own. Perhaps the same object photo with different background or photos with different object with the same background color. Another reason why you really need to use this kind of search is that you need the image in a bigger resolution / size.
To test the ability of this Google Image Search, you can download the thumbnail image of a Hello Kitty. I even used Screen Hunter to capture the thumbnail image (so that the quality may be lowered) I found through ordinary search. After that, I uploaded the captured image to Google Image Search and tried Search. The result was I could find the same image with different resolution. And through this way, you can get the higher resolution image for your own need.Another reason why people need to search by uploading images is that they want to know where his/her image can be found through the whole web through Google Image Search engine. The more places the image located means that the image is popular through the web cause many people share it.
