sometimes we look at a photo and miss on important information because we don't know all the facts or don't have the complete story behind it. captions give viewers important and relevant information about the photo. most of the time we will look at the photo for a second time after reading the caption under the photo and then find something different or new about it. this visual trip is also known as a loop.
captions differ from descriptions because they're meant to be read by someone else while descriptions contain basic information that will anyone who is working with them.