Angle's class III malocclusion is a condition where the mandible is positioned forward in relation to the maxilla, resulting in a reverse overjet. Features include a concave facial profile, mandible appearing well-developed, and a class III molar and canine relationship. Causes may be hereditary, functional habits, or skeletal asymmetries. Treatment depends on the patient's age, including growth modification in pre-adolescents using facemasks or chin cups, orthodontics in adolescents, and orthognathic surgery in adults using procedures like bilateral sagittal split osteotomy.