What's the difference between Kodak film 400 and 200?

The so-called 200-degree and 400-degree film refers to the sensitivity of the film, that is, the thickness of silver salt particles coated on the film. The higher the sensitivity, the thicker the silver salt particles, the stronger the ability to accept light, the higher the shutter speed when the light is insufficient, and the thicker the graininess of the picture. Therefore, high-sensitivity film is sometimes called "high-speed" film.