Nose hairs, as the name would suggest, are the bristly little hairs that grow inside one's nose. These hairs help to filter dust and other nastiness from the air before it can get into the lungs and cause trouble. They also serve to embarrass their owners (especially males) by poking out of the nostrils and into the world, and this is considered highly unattractive. There are really very few methods of dealing with overlong nose hair. The simplest method is a sharp, quick plucking, but to remove a nose hair in this fashion is quite excruciating and it will, without fail, make you sneeze, so be very careful when using tweezers for the plucking method. The other most accepted method is to use one of the variety of wondrous appliances designed for the specific purpose of trimming nose hair. The only problem is that this angers the nose hairs, which will quickly grow back with a vengeance.
So in short, there are three paths to choose: painful removal, frequent upkeep, or just live with nose hairs and be proud of who you are.
If you're going to be attending any social gatherings and would like to make a good impression, the third choice is probably not the best way to go.