What is it? Using an image file, Google Image Search reverse searches for other occurrences of the same or similar images on the web. This allows for the identification of other uses of the same image, or aspects of the same image, as one way to be able to find the source of an image and verify if the image has been tampered with.
How to use it to verify information: When using image.google.com, click on the camera icon to search by image, then either upload the URL with the image or the image file itself to return search results of other possible occurrences of the same or similar images. When using the Google Images add-on: the camera icon will appear on any searchable image on a webpage. Click on it to return search results.