What do you mean by long exposure?

Exposure is related to shutter, aperture and film sensitivity. Long exposure is a way to choose a slow shutter and a large aperture (small F value). The advantage is that you can take a clearer picture of the dim scenery. The sensitivity of film is fixed. If it is a digital camera, you can adjust the sensitivity to make the image clear, but high sensitivity will increase noise.

Ending: Long exposure is often used to shoot night scenes. By choosing a slow shutter and a large aperture.