I don't know where should we use photograph, where picture and where photo.
Are there and difference in meaning.
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When it comes to the image or visual representation of a person or thing produced on paper or a similar surface by a camera or photography, the words photograph, photo and picture are the same and used widely and interchangeably in our daily life.
Photo is the abbreviated form of photograph, which is more common in informal English.
As for the word picture, it can be used not only for a photograph but also for a painting or drawing. The image on the screen of TV, video, computer, is also a picture.
If you look up this word in a dictionary, you'll find many more meanings.