A doctor would use an otoscope to look at which part of the body?

An otoscope or auriscope is a medical device which is used to look into the ears. Health care providers use otoscopes to screen for illness during regular check-ups and also to investigate ear symptoms. An otoscope potentially gives a view of the ear canal and tympanic membrane or eardrum. Because the eardrum is the border separating the external ear canal from the middle ear, its characteristics can be indicative of various diseases of the middle ear space. The presence of earwax (cerumen), shed skin, pus, canal skin edema, foreign body, and various ear diseases can obscure any view of the eardrum and thus severely compromise the value of otoscopy done with a common otoscope, but confirm the presence of obstructing symptoms.

Source: Wikipedia