Orthodontics is a specialty of dentistry that is concerned with the study and treatment of malocclusions (improper bites), which may be a result of tooth irregularity, disproportionate jaw relationships, or both. The word comes from the Greek words ortho meaning straight and odons meaning tooth.
Orthodontic treatment can focus on dental displacement only, or can deal with the control and modification of facial growth. In the latter case it is better defined as "dentofacial orthopedics".
Orthodontic treatment can be carried out for purely aesthetic reasons improving the general appearance of patients' teeth and face for cosmetic reasons but treatment is often prescribed for practical reasons, providing the patient with a functionally improved bite (occlusion).
These are some pictures before & after treatment