A snapshot is a photograph that is “shot” spontaneously and quickly, most often without artistic or journalistic intent. They are commonly considered to be technically “imperfect” or amateurish-out of focus or poorly framed or composed (Wikipedia).
A photograph is a picture that is carefully composed with considerations of the lighting and position of a subject.
The difference between the two is that a snapshot is not as carefully composed while a photograph is more thoughtfully created.
Example 1- Snapshot:
This picture is a snapshot because the lighting is off and it is coming from the back. The frame looks crooked and the quality looks a little blurry.
Example 2- Snapshot:
This is also a snapshot because the picture just doesn’t seem to be carefully composed and it doesn’t follow and guides such as the rule of thirds.
Example 1- Photograph:
This is a photograph because the photographer considered the lighting and the position of the little girl. It is also evident that the picture was taken from a lower angle.
Example 2- Photograph:
In this photo the lighting was carefully considered because the figure has back-lighting. The figure is also not in the center of the picture which makes the photo visually pleasing.