It is all about uploading a particular image instead of a keyword for a search. By uploading a picture, you will be able to obtain more information about that image including individuals, objects or places in it. If not uploading the image then you can also give its URL to initiate the search.
Let’s talk in technical terms now! Image search or Reverse Image Search is a Content-based Image Retrieval (CBIR) technique, also known as Query by Image Content, which considers image content as a criteria of image search rather than the metadata information which contains image details such as camera that has been used, use of flash etc. On the other hand, CBIR technique considers several image aspects to perform image search such as texture, shape and color.
Search by image is a feature that makes use of “Reverse Image Search” which lets people to search for similar images simply by uploading an image using the ‘browse’ button or inserting the image URL. Search Engines Like Google, Bing, Yandex achieve this by evaluating the submitted picture and creating a calculated model of it using advanced procedures. It is then matched with numerous of other photos or images in Google, Bing or Yandex databases before returning matching and providing you with similar results. It should then be noted that whenever available, Google also makes use of meta-data about the image such as description.