The two holes in the human, are called nostrils. Even though they look the same, they do not act the same. They take turns swelling and tightening on the inside. One airway is smaller than the other, and air travels through that nostril more slowly. It allows us to breath, inhaling and exhaling oxygen from our lungs to hearts to our body, allowing our heart to involuntarily work and enable us to live. Also it provides us smelling ability, because particles in the air enter our nose. Which has special smell sensors.