Long Exposure Photography

Long exposure photography entails using a long-duration shutter speed to sharply capture the stationary elements of images while blurring, smearing, or obscuring its moving elements.
Technique
When a scene includes both stationary and moving subjects (for example, a fixed street and moving cars or a camera within a car showing a fixed dash-board and moving scenery), a slow shutter speed can cause interesting effects, such as light trails.