According to Michelle Robbins, who serves as Editor in Chief for Search Engine Land, today Google Images features will begin to incorporate captions for images that are found through Google Images searches on mobile devices, specifically for iOS and Android. Stated from the announcement of this update, the purpose of the update is to include more information that will help you easily understand what the image is about and if the website the image came from has more pertinent content for whatever you need. Titles from the pages that the images came from will be used as the image captions for now. As of now when I perform a Google Images search on my iPhone 6S, the only thing seen on the display page for a random search I performed is the URL below each image, which only tells you the websites the images came from. Upon clicking an image, you will see what appears to be sometimes the title of the page the image came from and then smaller text underneath. Once the update takes place, the images page for whatever you search will display a caption in bold font and not just the URL will be present.