Social media is a wretched hive of misinformation at times and it happens because we take a lot of what we see at face value. This is exploited by those who would make false or greatly exaggerated claims, such as people who want to be internet famous or who are trying to push their political or prejudiced opinions onto others. A popular tactic for this is to make an unsubstantiated claim (or lie) and find an existing photo somewhere online (e.g., Getty Images) that fits their false narrative.
TinEye is a reverse image search engine and a superb resource for separating fact from fiction. You provide it with an image (either upload one or via URL) and TinEye can find web pages that also use it, even if it has been modified. For iOS users, I've created two workflows that makes it easy to search for an image using TinEye. Both workflows require the use of a Dropbox account.
TinEye Photo is an action extension that accepts an image and temporarily stores it in your Dropbox folder. A public URL for the image is created and used as a TinEye search. Once you've seen the results, the workflow deletes the file from Dropbox.
The second workflow is TinEye URL, an action extension that accepts URLs. It gets the content of the URL, finds all images over 300px wide, and presents them all in a list for selection. The rest of the workflow is then the same as TinEye Photo.