Motion or movement in a visual image occurs when objects seem to be moving in a visual image.
In this photo of a waterfall, I see a waterfall rushing down moss covered rocks at a rapid rate. The Motion, can be seen in the waterfall. This Motion conveys a sense of rapid motion in my opinion. This image is appealing to me because it feels like the picture is going at amazing speeds.
In this photo of a tunnel, I see the tunnel as it curves and twists with its many rail lines curving. The Motion can be seen in the tunnel and the rail lines. This (descriptive Element of Art) conveys a sense of lightning fast speed in my opinion. This image is appealing to me because it makes you feel like you're going very fast at a speed you can't even define yourself.