I think 7 or 8 would mean classically attractive. Someone most feel the general population would agree is attractive. 9 or 10 is usually where "types" come into play. Those vary for each person, and is usually someone that all would classify as at least a 7 or 8, but crosses into 9 or 10 territory when it's your type.
Not necessarily, some people I look at and I can see why they would be attractive in a certain way. Like maybe they have really nice eyes and I know that they're generally considered attractive so they definitely are not ugly, but not quite my type. I would rate my type as a 10