What does photography often mean by exposure?

Two meanings. One is the "quantity" of light received by the photosensitive element mentioned by the buddy upstairs. Only when the photosensitive element receives the light can these light rays be reflected.

Another layer means that the undeveloped film was accidentally exposed when the film was used in the early days. This is called exposure. It should have been in the dark, but now it suddenly appears in the light. This is a bad thing. Now the entertainment section of the newspaper uses this meaning to describe the embarrassment of those stars. )