The laws of the exposure triangle allow for a perfectly exposed image but individually, all three components of the triangle allow for special in-camera effects that leave you with spectacular images and one of such effects is creating light trails with long shutter exposure.
Long exposure simply means reducing your shutter speed to allow more light into the camera. While a fast shutter freezes action, a slow shutter allows for that action to take its full course and that eventually results in some blur (regularly referred to as motion blur). If done properly, motion blur is always captivating and conveys the meaning of motion with a certain elegance and grace.
In this tutorial, Aidin Robbins breaks down the various ways you can manipulate the camera shutter and create stunning imagery ranging from motion blur and the way to Astrophotography.