Occupational therapy deals with mental strength and fine motor skills like writing and grasping objects, while physical therapy focuses on physical strength and general motor skills like walking. Both fields sometimes work together, such as when a patient is paralyzed - the physical therapist teaches wheelchair mobility and the occupational therapist helps with hand skills. The main difference is that occupational therapy addresses mental and fine motor abilities, while physical therapy concentrates on physical strength and gross motor functions for everyday living.