"We are what we do" sounds like bartender's wisdom but it is an observation attributed to Aristotle. Work is often the single biggest influence in our lives, more than friends, lovers and family. It takes up the most time, is the subject of the most thought. This is particularly true in the United States where work is often the only thing that unites a varied (or fractures, depending on your point of view) culture.
It's impossible to separate the faces in some of these pictures from their occupations. To a New Yorker, the man in "FDNY Ladder Company No. 2" is a firefighter in every drop of his being. The woman in "Smoking Break," on the other hand, is mysterious and hard to place. So when we learn that she works in a wig store in the Garment District, she suddenly makes sense.
It helps to know that Willets Point is a graceless part of Queens that houses hundreds of auto repair shops, junkyards, and chop shops. Once you know that, it's easy to tell that these are the men who can find a taillight to a 1976 Ford F150 pickup truck. In a every sense of the phrase, they are what they do.