Hi, I'd like some help please. I see F1, F2 and then "This one is an F3"...F4 etc in relation to certain breeds while I'm reading posts. It makes no sense to me, as I don't know what any of those are supposed to mean. The only thing I see is "tornado" when reading that. Can someone please explain to me what word the "F" is supposed to stand for, and what the numbers themselves mean also? I'd really appreciate it.