If a guy calls you attractive, then he thinks you are attractive. It could possibly mean that he likes you but there are a few who would say that just because they can and they actually don't like you in any particular way more than a friend. So just take it as a compliment and move on from it. Don't ponder on it too much until he brings it up again or something like that. You don't want to make the assumption that he likes you when that may not always be the case.
And physical attractiveness differs from person to person. There really isn't a standard set of physical characteristics that make a person attractive. Each person has their own set, so I can't say. Plus sometimes, we even find people who are not within our type attractive as well. That's why it's really hard to say.