Does the cinema show movies on film? How do you synchronize the picture with the sound?

At present, movies and digital movies coexist, and the sound of movies and movies is recorded on the edge of the film. When the film is shown, special audio light is projected on the audio band at the edge of the film, and the sound is transmitted to the public address system synchronously, and then to the audience through the speaker. Digital film is a complex high-tech electronic system, which only professional researchers can explain clearly. Digital film is the inevitable trend of the development of science and technology, and it will definitely replace film film in the near future.