This is a facial cosmetic procedure, often performed to enhance the appearance of the nose. During rhinoplasty, the nasal cartilages and bones are modified, or tissue is added. The aim is to improve the visual appeal of the nose.
Rhinoplasty is also frequently performed to repair nasal fractures. When rhinoplasty is used to repair nasal fractures, the goal is to restore pre-injury appearance of the nose.
As noted, the term "nose job" is slang so it is not in most standard medical dictionaries although it is in very common use.