Long exposure is a photography technique that involves using a slow shutter speed to capture stationary elements in a scene while allowing any moving elements to blur. This technique is commonly used in night photography to create light trails from moving vehicles, in water photography to achieve a smooth and dreamy effect on water surfaces, and in various other scenarios where capturing motion or creating a sense of time passing is desired. Long exposure photography requires a tripod to avoid camera shake and often involves experimentation with different shutter speeds to achieve the desired effect.