Welcome to film photography.

None of that is actually specific to film photography. The same applies to digital photography as well. ISO says how sensitive your film is to the light. Aperture and shutter speed combined with the light reflected from your subject defines how much light will actually hit the film.

For example...
Let's say your subject is well lit in day light sun.
Let's say your film is ISO 400.
Let's say your shutter speed is 1/400.
Let's say your aperture is about f/16.

Then, you are LIKELY to get a good exposure.

Because your shutter speed and aperture combined defines the amount of light that will hit your film, the combination that will work is actually endless.
You could increase the shutter speed and decrease the aperture opening or do the other way around. There's a simple math to it (but I won't go into that now)

Does that help at all? This is very basic, yet a very important aspect of photography. Because combination is endless, there isn't a single example that will explain all. Actually, there's a mathematical formula for it as well. I'd say this is a scientific part of an artistic field of photography. It is possible to do it by feel but for complete understanding, it requires a bit of logical approach.