It varies by individual, as well as culture, country and continent. In many parts of the world, there is the "white" standard of beauty, generally speaking it applies to advertising rather than society. In modeling, whites are not the standard of beauty, instead, and exotic look is.
The most common characteristics of beauty are:
-Straight white teeth
-Clear healthy skin
-Healthy, soft manageable hair
There are some parts of the world where being overweight is desired, such as Morocco(I believe) and I'm sure these do not all apply, they are simply examples.
I think "beauty" has a lot to do with the person's particular tastes. However, I do believe that some people are thought of as beautiful by more people than others. But I also believe that everyone has their own beauty somewhere (no matter how clichéd that sounds).
Good question. Everyones view of beauty can difr. Yes there are people that many people can consider beautiful, but that person may not be beautiful to others. Just the same, someone may find beauty in someone that other people had not seen. It goes both ways. It is definitely an opinion.
I think it's a little bit of both. Personal opinion influences who and what we find beautiful a great deal, but there is also a subconscious attraction to traits that signify good health, due to our basic desire to mate and reproduce. It's a well-known fact that many celebrities and models that are considered beautiful, handsome, etc, have a face that is perfectly symmetrical, and fits the "Golden Ratio". Symmetry ensures unrelated lineage and therefore is more likely to produce healthy offspring. There's definitely a science to beauty.