"What do you see in the photo?"
Translation:Kion vi vidas en la foto?
Lukas, the difference is that "bildo" is like "picture" and "foto" is like "photo".
A photo is always a picture but a picture is not always a photo.
Pictures is many types of mediums to show an image from painting to photographs. A photo is taken by camera of some sort to create an image, or a picture.
Hope that helps!