> I didn't know if it was some composition style, or focus effect, or anything else

It's all of that and more. Her technique in exposure, action. composition is wonderful. However as I am browsing her portfolio I keep finding myself delighted in her ability to reveal hidden worlds in the mundane.

Take for example this child playing in the dirt. He's been caught in the act, of what is surely an innocuous game. But he is wearing a jumpsuit, a coonskin cap and has a pack of matches, it speaks of so much mischief. http://www.vivianmaier.com/portfolios/travels/?pid=122