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