I'm not sure if I completely understand what you're asking for, but I think that you want an explanation for what ISO and F-stop is? Well, i'll give you the simple answer. The higher the ISO, the less light required to properly expose a picture. But of course, the higher you go in ISO, the more grain you get. So with ISO400, you can shoot a picture with less light than the ISO100 film would require. The "f number" is the f-stop. It basically refers to the size of the aperture in the lense(how big the opening is). The lower the number(let's say f/2.5), the wider the opening is and hence you can take a picture with a higher shutter speed(so f/11 would be a smaller opening than f/2.5). But as you make your aperture bigger, you're shortening your depth of field(meaning that less will be in focus). I hope this was the answer you were looking for.
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