The nose helps us to breathe, smell, filter air that travels to our lungs and also helps us to taste. That's why when we have a stuffy nose, we often feel like we can't breathe easily, smell anything or taste as well.

The main function of the nose is to help us breathe. When we inhale through our nose, air passes through our nostrils into a short and narrow area known as the nasal passage that leads to the back of the throat (pharynx), and on down into the windpipe and lungs. From there it continues throughout the respiratory system.

When we breathe through our nose, there are advantages that we don't get when we breathe through our mouth. The nose has ancillary hairs that catch airborne particles that we don't want to reach our lungs.

Nose hairs also filter out viruses, which typically attach themselves inside the nostrils. Think of the nose as a guard to keep harmful things out of our bodies. These particles mix with natural secretions and are transported into the throat for elimination in the stomach. The external air that we breathe is also warmed and moistened as it passes through the nose.

We are able to smell as the air flows through the nose and over structures called turbinates in the nasal cavity. The turbinates slow the air and direct it toward the olfactory epithelium, where odor molecules reach olfactory receptor neurons that send electrical impulses to our brain. Remarkably, the brain can recognize tens of thousands of odors from our past and instantly reminds us what we are smelling.

Source: http://www.experiencefestival.com/a/NOSE_-_Function/id/596704