What is the difference between photo and image?
A "photo" is something that was taken with a camera.
Short for "Photograph". Photo means 'light'.
An "image" is something generated or a representation of something in any other way.
All elephants are gray things, but not all grey things are elephants. All photos are images, but not all images are photos.
Every photo is also an image, but not every image is a photo. An image can also be a drawing, a vector graphic, a bitmap file, many more. The distinction also very much depends on the context. In software, images and photos belong to the same group of objects and behave similarly, for example when placing an image/photo into a document or on a web site.