Long exposure photography is simply the use of a long-duration shutter speed when taking a photograph. This technique is commonly used in poor light conditions or at night because more light can be absorbed by leaving the camera’s shutter open for a longer period of time.
The basic concept is that, the longer you leave the shutter open, the brighter the image will become. So this is a very useful technique when taking photographs in low light conditions.
One main point to note when taking a long exposure shot, is that anything that moves while the camera’s shutter is open will become blurred. For this reason, it is strongly suggested that you use a tripod when producing a long exposure photograph.