Attraction between people is an odd thing; it can spark many emotions that may lead to different kind of relationships. There are many different factors that come into play when determining if someone is attractive. These factors include how close someone is in terms of distance, the amount of similarities are present, if one is willing to reciprocate feelings of attraction, and simply how one's physical appearance appeals to another.
This video shows how physical attraction plays more of a role than we know, and that there are certain features that one may find more attractive. For example, for a man, a larger jawbone portrays a more attractive man, for the correlation between testosterone and other hormones specific to males are more present with this feature. Even though humans do not specifically note the fact of hormones and "manliness," the fact that our brains recognize this important correlation proves the idea that physical attraction in first impressions plays a great role in how attractive one appears to another.
These concepts are important in real life because it shows how inclined people are to finding a mate. People worry about these things every day; there are dating sites, advice columns, and many other forms of media to try and help people find a mate. The bottom line is that no one factor will determine if someone is attractive to another; there is no simple formula for determining who will be right for whom in the game of finding someone to spend a lifetime with.