I'll explain it as best as I can. Not that it's complicated at all, just maybe confusing to people who aren't used to working with cameras.
When you take a picture with a film camera, the shutter opens up in the lense, allowing the light from whatever you're taking a picture of to shine on the film. That, my friends, is called exposure. When it's really bright out, you only need a very short one. When it's darker, there's a longer exposure time. In most scenarios, the difference is that of maybe a milisecond or two.
Now, see, this is what RioVonDick (https://www.deviantart.com/riovondick) and I did. The shortest exposure time I think we had was about five seconds, which is e